Running: a great sport to start in later life

Lots of people start running in their 30s or older, and it is one of the few sports in which you can improve with age – and even progress to elite level

'Age is far less of a barrier to improvement in running than it is in other sports.' 

For many people reminiscing about their childhood sporting memories, the first activity that springs to mind is the dreaded cross-country run. Images of cold, wet days spent slogging around muddy fields; the sound of sadistic PE teachers barking instructions still ringing in the ear. These are not fond memories. Indeed, running was, and still is, frequently viewed as a punishment; the sort of thing that no child in their right mind would want to do voluntarily, let alone enjoy.

One of the ironies of the current boom in participation is that while unprecedented numbers of people are taking up running, many of these people are in their 30s or above. It was hoped that the 2012 Olympics would "inspire a generation" – but it wasn't really part of the plan for that generation to be aged 30-60. Recent reports suggest that child fitness levels still aren't what they should be, with nearly half of all children not taking the government's recommended one hour of exercise a day.

Although any new runners are fairly good news for public health officials, the age profile of the current crop means they are less likely to make inroads into the thorny issue of running "standards". It has been well documented that times are generally slower now than they were in the 80s, but the fact that runners are starting older doesn't always mean that they can't pop up at the sharp end of races.

Running is one of the few sports at which it is possible, albeit with a lot of hard work and a bundle of talent, to progress to elite status despite only taking it up in your 30s. One of the best examples is the great Jack Foster, the Liverpool-born New Zealander and self-styled "ancient marathoner", who pulled on a pair of trainers for the first time at the age of 32 and by age 40 found himself running 2:11 for the marathon, picking up a silver medal for his efforts at the Christchurch Commonwealth Games in 1974.

At a slightly lower level, Welshman Martin Rees this year became the proud holder of the age 60 World Best times for the half marathon (71:30) and 10km (32:54), after a glorious couple of decades during which heas run incredible times over a full range of distances from 5k (14:20) to the marathon (2:23). He only took up the sport in his late 30s and soon got the running bug.

Of course, while we all may hold secret hopes of uncovering an latent talent, most of us are unlikely to progress to the very front of the pack. But the exploits of the likes of Foster and Rees are relevant to all of us, whether we like to race on a weekend or prefer to battle our own limitations on solitary excursions through the countryside.

The message is that age is far less of a barrier to improvement in running than it is in other sports. While the amateur footballer is confronted, aged 40, with his or her place in the team being given to the latest young talent, the amateur runner is often just getting going.

With running, especially if taken up later in life without any previous experience, it really is realistic to expect to improve with age – albeit with some upper limit, though Rees seems to be getting faster and faster. It is this expectation that can ensure the motivation to continue remains well into our senior years.

Who knows where it will take you? The never-ending setting of targets and the tangible results keep us coming back for more and more.

Dean Karnazes: the man who can run for ever

Most runners have to stop when they reach their lactate threshold, but Dean Karnazes' muscles never tire: he can run for three days and nights without stopping. What's his secret?

 

 

 

From club runners to Olympians, every athlete has a limit. Scientifically, this limit is defined as the body's lactate threshold and when you exercise beyond it, running rapidly becomes unpleasant. We've all experienced that burning feeling – heart pounding, lungs gasping for air – as your muscles begin to fatigue, eventually locking up altogether as your body shuts down. However, there is one man whose physiological performance defies all convention: Dean Karnazes is an ultrarunner from California and, at times, it seems as if he can run forever.

Karnazes has completed some of the toughest endurance events on the planet, from a marathon to the South Pole in temperatures of -25C to the legendary Marathon des Sables, but in his entire life he has never experienced any form of muscle burn or cramp, even during runs exceeding 100 miles. It means his only limits are in the mind.

"At a certain level of intensity, I do feel like I can go a long way without tiring," he says. "No matter how hard I push, my muscles never seize up. That's kind of a nice thing if I plan to run a long way."

When running, you break down glucose for energy, producing lactate as a byproduct and an additional source of fuel that can also be converted back into energy. However, when you exceed your lactate threshold, your body is no longer able to convert the lactate as rapidly as it is being produced, leading to a buildup of acidity in the muscles. It is your body's way of telling you when to stop – but Karnazes never receives such signals.

"To be honest, what eventually happens is that I get sleepy. I've run through three nights without sleep and the third night of sleepless running was a bit psychotic. I actually experienced bouts of 'sleep running', where I was falling asleep while in motion, and I just willed myself to keep going."

While supreme willpower is a common trait among ultrarunners, Karnazes first realised that he was actually biologically different when preparing to run 50 marathons in 50 days across the US back in 2006. "I was sent to a testing center in Colorado," he recalls. "First, they performed an aerobic capacity test in which they found my results consistent with those of other highly trained athletes, but nothing extraordinary. Next, they performed a lactate threshold test. They said the test would take 15 minutes, tops. Finally, after an hour, they stopped the test. They said they'd never seen anything like this before."

As Laurent Messonnier from the University of Savoie explains, the difference is that your aerobic capacity is a measure of your cardiovascular system performance, while your lactate threshold is your ability to clear lactate from your blood and convert it back into energy.

"If you take a high-level runner and you train that guy for a long time, his cardiovascular system will improve until a certain point where it will be very difficult to improve it further, as it's determined by the heart and the blood vessels. So if you carry on training that guy, you will not improve his aerobic capacity but his performance will still improve, because the lactate threshold is not limited by the cardiovascular system – it's determined by the quality of the muscles."

Your body clears lactate from the blood via a series of chemical reactions driven by the mitochondria in your muscle cells. These reactions transform lactate back to glucose again and they are enhanced by specific enzymes. The clearance process also works more efficiently if your mitochondria have a larger capacity, increasing their ability to use lactate as a fuel.

Years of training will improve both your enzymes and mitochondria and so improve your clearance, but there is a limit to how much you can improve your lactate threshold by training alone. If you inherit these enzymes and a larger mass of mitochondria genetically, your personal limits will be far higher.

Karnazes fell in love with running from an early age, and at high school he began to show endurance capabilities which far surpassed those of his peers. At one charity fundraiser, while his fellow runners were able to manage 15 laps of the track at most, Karnazes completed 105. But in his mid-teens he stopped altogether until experiencing an epiphany on his 30th birthday. Gripped by a powerful desire to run once more, he set off into the night.

After 15 years of no training, most of us would not have been physically capable of getting too far, but Karnazes did not stop until 30 miles later. Although the blisters were excruciating, his muscles showed little sign of fatigue.

"Many elite distance runners will show some improvements in their ability to clear lactic acid from the system due to the 'training effect', but that only goes so far," he says. "The rest, as I am told, is left up to heredity. They say the best thing you can do as a long-distance runner is to choose your parents well!"

However, genetics alone does not tell the full story. Karnazes believes that his lactate clearance abilities could also be down to low body fat, low sweat rate, a highly alkaline diet and low exposure to environmental toxins. Genetics can give you the propensity for a natural advantage but you express your genes differently depending on your environment and your lifestyle.

The intriguing question is whether Karnazes' lactate clearance abilities would be the same now if he had not done so much running at an early age.

"If you take two twins – one grows up in Africa and one grows up in northern Europe – their athletic performance will potentially be very different, because they will express their genes differently as the environment, food, everything is different," Messonnier says.

An interesting experiment could be to repeat the lactate threshold test with Karnazes' brother.

"He plays competitive volleyball but has never really done an extensive amount of running," Karnazes says. "I would be curious if he exhibits some of those same abilities to clear lactic acid from his system."

Taking aim at belly fat

Unlike fat parked on the hips and thighs, fat around the middle produces substances that can create serious health risks.

No matter what your body shape, excess fat isn't good for your health. But saddlebags and ballooning bellies are not equivalent. When it comes to body fat, location counts, and each year brings new evidence that the fat lying deep within the abdomen is more perilous than the fat you can pinch with your fingers.

In most people, about 90% of body fat is subcutaneous, the kind that lies in a layer just beneath the skin. If you poke your belly, the fat that feels soft is subcutaneous fat. The remaining 10% — called visceral or intra-abdominal fat — lies out of reach, beneath the firm abdominal wall. It's found in the spaces surrounding the liver, intestines, and other organs. It's also stored in the omentum, an apron-like flap of tissue that lies under the belly muscles and blankets the intestines. The omentum gets harder and thicker as it fills with fat.

Although visceral fat makes up only a small proportion of body fat, it's a key player in a variety of health problems.

As women go through their middle years, their proportion of fat to body weight tends to increase — more than it does in men — and fat storage begins favoring the upper body over the hips and thighs. Even if you don't actually gain weight, your waistline can grow by inches as visceral fat pushes out against the abdominal wall.

Where's the fat? Visceral fat lies in the spaces between the abdominal organs and in an apron of tissue called the omentum. Subcutaneous fat is located between the skin and the outer abdominal wall.

The trouble with visceral fat

Body fat, or adipose tissue, was once regarded as little more than a storage depot for fat blobs waiting passively to be used for energy. But research has shown that fat cells — particularly visceral fat cells — are biologically active. "One of the most important developments [since the mid-1990s] is the realization that the fat cell is an endocrine organ, secreting hormones and other molecules that have far-reaching effects on other tissues," says Dr. Barbara B. Kahn, chief of the division of endocrinology, diabetes, and metabolism at the Beth Israel Deaconess Medical Center in Boston.

Before researchers recognized that fat acts as an endocrine gland, they thought that the main risk of visceral fat was influencing the production of cholesterol by releasing free fatty acids into the bloodstream and liver. We now know that there's far more to the story. Researchers have identified a host of chemicals that link visceral fat to a surprisingly wide variety of diseases.

Subcutaneous fat produces a higher proportion of beneficial molecules, and visceral fat a higher proportion of molecules with potentially deleterious health effects. Visceral fat makes more of the proteins called cytokines, which can trigger low-level inflammation, a risk factor for heart disease and other chronic conditions. It also produces a precursor to angiotensin, a protein that causes blood vessels to constrict and blood pressure to rise.

Researchers at Harvard have discovered that, compared with subcutaneous fat, visceral fat secretes more of retinol-binding protein 4 (RBP4), a molecule that increases insulin resistance. As the volume of visceral fat increases, so do levels of RBP4. The connection is so strong that researchers are developing a blood test for RBP4 as a way for physicians to measure an individual's store of visceral fat.

Subcutaneous fat produces more of certain beneficial molecules, including the hormone leptin, which acts on the brain to suppress appetite and burn stored fat. Adiponectin, another hormone produced mainly by subcutaneous fat, helps protect against diabetes by regulating the processing of fats and sugars; it also has an anti-inflammatory effect on the linings of blood vessels. (Adiponectin is made by visceral fat, too, but production falls as fat volume increases.)

Gut check A tape measure is your best home option for keeping tabs on visceral fat. Measure your waistline at the level of the navel — not at the narrowest part of the torso — and always measure in the same place. (According to official guidelines, the bottom of the tape measure should be level with the top of the right hip bone, or ilium — see the illustration — at the point where the ilium intersects a line dropped vertically from the center of the armpit.) Don't suck in your gut or pull the tape tight enough to compress the area. In women, a waist circumference of 35 inches or larger is generally considered a sign of excess visceral fat, but that may not apply if your overall body size is large. Rather than focus on a single reading or absolute cut-off, keep an eye on whether your waist is growing (are your pants getting snug at the waist?). That should give you a good idea of whether you're gaining unhealthy visceral fat.

From fat to disease

Visceral fat can be measured in a variety of ways. CT scans and full-body MRIs are the most precise, but they are expensive and rarely available, so investigators often use estimates based on waist circumference or waist size in proportion to height (see "Gut check"). To ensure that they're not just measuring overall obesity, researchers also check whether a person's waist circumference is higher than average for her or his body mass index (BMI).

Visceral fat is implicated in a number of chronic conditions, including these:

Cardiovascular disease. Several studies have documented this effect. For example, a large study of European women ages 45 to 79 concluded that those with the biggest waists (and those with the largest waists in relation to their hip size) had more than double the risk of developing heart disease. The risk was still nearly double even after adjustment for several other risk factors, including blood pressure, cholesterol, smoking, and BMI. Even in healthy, nonsmoking women, every 2 inches of additional waist size raised the risk for cardiovascular disease by 10%.

Higher visceral-fat volume also has a deleterious impact on several other heart disease risk factors. It tends to increase blood pressure and blood sugar levels, raise triglyceride levels, and lower levels of HDL (good) cholesterol. Taken together, these changes, known as metabolic syndrome, create a serious risk for cardiovascular disease and type 2 diabetes. In 2009, a consensus group of medical professional organizations agreed that abdominal obesity should be recognized as a major feature of metabolic syndrome.

Dementia. Researchers at Kaiser Permanente found that people in their early 40s with the highest levels of abdominal fat, compared with those who had the least abdominal fat at that age, were nearly three times more likely to develop dementia (including Alzheimer's disease) by their mid-70s to early 80s. Dementia was not associated with increased thigh size.

Asthma. In a large study of California teachers, women with high levels of visceral fat (a waist circumference of more than 35 inches) were 37% more likely to develop asthma than women with smaller waists — even if their weight was normal. The risks were highest for women who were both large-waisted and overweight or obese. The investigators believe that belly fat raises the risk of asthma more than other poundage because it has inflammatory effects throughout the body, including in the airways.

Breast cancer. A combined analysis of several studies found that premenopausal women with abdominal obesity (the largest waist size in proportion to their height) were at greater risk for breast cancer. Large waists were also linked to breast cancer risk among postmenopausal women, but that effect was not significant once BMI was taken into account.

Colorectal cancer. People with the most visceral fat have three times the risk of developing colorectal adenomas (precancerous polyps) than those with the least visceral fat, according to a Korean study in theAmerican Journal of Gastroenterology (January 2010). The relationship was found after many other risks were accounted for. The researchers also confirmed that adenomatous polyps in the colon are associated with insulin resistance, which may be the mechanism that increases the cancer risk.

Keeping visceral fat at bay

Where you tend to gain fat depends on your genes, your hormones, your age, your birth weight (smaller babies more readily add belly fat later in life), and whether you've had children (women who have given birth tend to develop more visceral fat than women who haven't).

As young adults, women on average have less visceral fat than men, but that changes with menopause. In a four-year study at Louisiana State University tracking healthy middle-aged women, every one of them put on some subcutaneous belly fat, but only those who entered menopause added significant amounts of visceral fat. Lowered estrogen levels (which increase the proportional influence of testosterone) contribute to the shift toward a male pattern.

You can't change your birth weight or your genes, and you can't hold off menopause. (Studies are mixed about whether hormone replacement therapy influences visceral fat gain.) But there are several ways you can minimize the accumulation of visceral fat. The good news is that because it's more readily metabolized into fatty acids, it responds more efficiently to diet and exercise than fat on the hips and thighs. Here are some approaches that may help:

Keep moving. Exercise can help reduce your waist circumference. Even if you don't lose weight, you lose visceral fat and gain muscle mass. In the Louisiana study, the women going through menopause (those who gained visceral fat) also became less physically active.

Engage in at least 30 minutes of moderate-intensity activity most days, such as brisk walking or bicycling at a casual pace. Also, Kahn suggests, create opportunities to add motion to routine tasks. For example, park farther from your destination and walk the rest of the way, take the stairs instead of the elevator, and stand while you talk on the phone.

Studies have shown that you can help trim visceral fat or prevent its growth with both aerobic activity (such as brisk walking) and strength training (exercising with weights). Spot exercises, such as sit-ups, can tighten abdominal muscles but won't get at visceral fat.

Exercise can also help keep fat from coming back. In a study at the University of Alabama, Birmingham, dieting women lost an average of 24 pounds and reduced both visceral and subcutaneous fat, with or without aerobic or strength-training exercise. In the following year, those who maintained their exercise programs — a modest 40 minutes twice a week — maintained their visceral fat loss, while those who didn't exercise or abandoned their programs showed a 33% average increase in visceral fat.

Eat right. Choose a balanced diet that helps you achieve and maintain a healthy weight. Include plenty of calcium: according to another study from the University of Alabama, Birmingham, the more calcium a woman consumes, the less visceral fat she gains. Avoid products that seem to encourage belly fat deposition, including trans fats (hydrogenated vegetable oils) and fructose-sweetened foods and beverages.

Don't smoke. The more you smoke, the more likely you are to store fat in your abdomen rather than on your hips and thighs.

Get your sleep. Too little is bad. A five-year study found that adults under age 40 who slept five hours or less a night accumulated significantly more visceral fat. But too much isn't good, either — young adults who slept more than eight hours also added visceral fat. (This relationship wasn't found in people over age 40.)

Mind your mood. In the Study of Women's Health Across the Nation, middle-aged women who showed more hostility and had more depressive symptoms also had more visceral fat — but not more subcutaneous fat. In other studies, higher levels of the stress hormone cortisol were associated with a buildup of visceral fat even in lean women.

Making the Case for Eating Fruit

Experts agree that we are eating too much sugar, which is contributing to obesity and other health problems. But in the rush to avoid sugar, many low-carb dieters and others are avoiding fruits. But fresh fruit should not become a casualty in the sugar wars, many nutrition experts say.

Dr. David Ludwig, the director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, said that sugar consumed in fruit is not linked to any adverse health effects, no matter how much you eat. In a recent perspective piece in The Journal of the American Medical Association, he cited observational studies that showed that increased fruit consumption is tied to lower body weight and a lower risk of obesity-associated diseases.

Whole fruits, he explained, contain a bounty of antioxidants and healthful nutrients, and their cellular scaffolding, made of fiber, makes us feel full and provides other metabolic benefits. When you bite into an apple, for example, the fruit’s fiber helps slow your absorption of fructose, the main sugar in most fruits. But fiber is not the full story.

“You can’t just take an 8-ounce glass of cola and add a serving of Metamucil and create a health food,” Dr. Ludwig said. “Even though the fructose-to-fiber ratio might be the same as an apple, the biological effects would be much different.”

Fiber provides “its greatest benefit when the cell walls that contain it remain intact,” he said. Sugars are effectively sequestered in the fruit’s cells, he explained, and it takes time for the digestive tract to break down those cells. The sugars therefore enter the bloodstream slowly, giving the liver more time to metabolize them. Four apples may contain the same amount of sugar as 24 ounces of soda, but the slow rate of absorption minimizes any surge in blood sugar. Repeated surges in blood sugar make the pancreas work harder and can contribute to insulin resistance, thereby increasing the risk for Type 2 diabetes.

“If we take a nutrient-centric approach, just looking at sugar grams on the label, none of this is evident,” Dr. Ludwig said. “So it really requires a whole foods view.”

Fruit can also help keep us from overeating, Dr. Ludwig said, by making us feel fuller. Unlike processed foods, which are usually digested in the first few feet of our intestines, fiber-rich fruit breaks down more slowly so it travels far longer through the digestive tract, triggering the satiety hormones that tend to cluster further down the small intestines.

Another nutrition expert, Dr. Robert Lustig, a professor of pediatrics at the University of California, San Francisco, who has called sugar “toxic” at high doses and fructose the most “actionable” problem in our diet, is still a fan of fruit. “As far as I’m concerned, fiber is the reason to eat fruit,” since it promotes satiety and the slow release of sugar. He adds a third benefit from fiber: it changes our “intestinal flora,” or microbiome, by helping different species of healthy bacteria thrive.

Neither doctor favors certain fruits over others. But Dr. David L. Katz, director of the Yale University Prevention Research Center, said that “to maximize the benefit, you actually want a variety” of fruits. He advises “eating the rainbow,” since different colors signal different types of antioxidants and nutrients.

All three experts caution against choosing juice over whole fruit. While the best juice has nothing added, nothing subtracted, some important changes take place when you turn fruit into liquid. Chewing the whole fruit slows down consumption, Dr. Katz said, compared to when you “take an 8-ounce juice and just pour it down the hatch,” which not only makes it easier to ingest more calories, but releases fructose faster into the bloodstream.

Plus, he said, with juicing, “you reduce some of the metabolic benefit of the fiber by pulverizing it so fine; it changes the physical structure.” Commercially produced juices are particularly concerning since they are often filtered, removing fiber altogether. If you opt for juice, tossing whole fruit in a blender rather than squeezing it offers the best chance of retaining most of the fiber, vitamins and minerals.

Dried fruits also hold one of the main disadvantages of juices: volume. Dried fruit essentially concentrates the calories and sugar into smaller packets, making it easier to consume excess calories. But dried fruit is better than juice, Dr. Katz said, because it preserves the fruit’s cellular structure, along with the health assets that provides. And since dried fruit travels easily and does not rot, it can make the difference in eating any fruit at all.

Dr. Katz’s hierarchy? Fresh fruit, followed closely by dried fruit, with sweetened dried fruit a distant third, and juice in fourth place.

He said we should remember “a law we all learned from Aesop” and judge fructose “by the company it keeps,” fiber and all.

Toward a Diet That Prevents Cancer

New research says eating in accordance with the "Dietary Guidelines for Americans" correlates with lower risks of pancreatic cancer

It's pretty well-established that smoking, obesity, and being sedentary increase our risk of pancreatic cancer. The relationship to diet is debated. People with lower levels of lycopene and selenium in their blood, for example, seem to be at higher risk — though we don't have evidence that we should be taking lycopene and selenium supplements. There's a lot of lycopene in fruit, and some studies tell us that eating more fruit and vegetables seems to be good, but that association hasn't held up in every study. Many blame the "Western" diet (high intake of fat and/or meat, particularly smoked or processed meats, refined grains, and sugars and lower intakes of fruits, vegetables, and whole grains) as a risk factor — especially because rates of pancreatic cancer are so, much higher in Western countries than many other parts of the world — though that variable also hasn't held up in prospective studies. 

So it's good to see a solid study out this week in the Journal of the National Cancer Institute that tells we seem to be on the right track diet-wise.

As you probably know, every five years since 1980 the U.S. government has issued new Dietary Guidelines for Americans. That once included acknowledging the now-infamous 1958 carb-based food pyramid. (But that was the 80s, when carbs were good.)The guidelines since are increasingly based in research and evidence. They'll continue to change as we learn more. They aren't specifically meant to protect us from cancer; just to get us as healthy as possible.

So Dr. Hannah Arem and a team at the National Institutes of Health wanted to see if we're on the right track. They calculated the Health Eating Indices (HEIs) of 537,218 people based on the guidelines (the 2005 version, which has since been lightly updated, in 2010), and then compared them to pancreatic cancer rates. 2,383 people ended up getting pancreatic cancer, but they were 15 percent less likely to get it if they had the highest HEIs as compared to the lowest. Arem's team controlled for other variables like diabetes and smoking. 

According to Arem and colleagues, “[these] findings support the hypothesis that a high-quality diet may also play a role in reducing pancreatic cancer risk.”

Health Eating Index scoring

(USDA, 2005)

In accompanying commentary, Drs. Rachel Ballard-Barbash and Susan Krebs-Smith of the National Cancer Institute, along with Dr. Marian Neuhouser from the Hutchinson Cancer Research Center, seem on board with the study. They write, in long sentences, "Food based indices such as the HEI may provide a superior and more comprehensive analytic approach to characterizing our complex diets and their association with health outcomes compared with reductionist approaches focused on single foods or isolated nutrients."
(They're talking to you, lycopene!)
Arem made the same point in the original article: "There may be biologic interaction or synergy between different nutrients and/or dietary constituents/components that is not captured when assessing single foods or nutrients." So their conclusion is the bigger-picture "consuming a high-quality diet may reduce the risk of pancreatic cancer."
It's too bad we can't shake our fists at, or fill our totes with, one or two specificfoods/nutrients. But with diet that's rarely the case, and at least now we can feel like we're doing something right (or wrong). Pancreatic cancer can be terrifying, so even if only as a conceptual step toward more progress and reassurance, this is not nothing.
Here is where we stand on defining "high-quality diet" as a country—the highlights of the 2010 guidelines:

• Increase vegetable and fruit intake.

• Eat a variety of vegetables, especially dark-green and red and orange vegetables and beans and peas.

 

• Consume at least half of all grains as whole grains. Increase whole-grain intake by replacing refined grains with whole grains.

 

• Increase intake of fat-free or low-fat milk and milk products, such as milk, yogurt, cheese, or fortified soy beverages.

 

• Choose a variety of protein foods, which include seafood, lean meat and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds.

 

• Increase the amount and variety of seafood consumed by choosing seafood in place of some meat and poultry.

 

• Replace protein foods that are higher in solid fats with choices that are lower in solid fats and calories and/or are sources of oils.

 

• Use oils to replace solid fats where possible.

 

• Choose foods that provide more potassium, dietary fiber, calcium, and vitamin D, which are nutrients of concern in American diets. These

foods include vegetables, fruits, whole grains, and milk and milk products."

This Is How Your Brain Becomes Addicted to Caffeine

Within 24 hours of quitting the drug, your withdrawal symptoms begin. Initially, they’re subtle: The first thing you notice is that you feel mentally foggy, and lack alertness. Your muscles are fatigued, even when you haven’t done anything strenuous, and you suspect that you’re more irritable than usual.
Over time, an unmistakable throbbing headache sets in, making it difficult to concentrate on anything. Eventually, as your body protests having the drug taken away, you might even feel dull muscle pains, nausea and other flu-like symptoms.
This isn’t heroin, tobacco or even alcohol withdrawl. We’re talking about quitting caffeine, a substance consumed so widely (the FDA reports that more than 80 percent of American adults drink it daily) and in such mundane settings (say, at an office meeting or in your car) that we often forget it’s a drug—and by far the world’s most popular psychoactive one.
Like many drugs, caffeine is chemically addictive, a fact that scientists established back in 1994. This past May, with the publication of the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM), caffeine withdrawal was finally included as a mental disorder for the first time—even though its merits for inclusion are symptoms that regular coffee-drinkers have long known well from the times they’ve gone off it for a day or more.

Photo by Flickr user Simon le nippon

Why, exactly, is caffeine addictive? The reason stems from the way the drug affects the human brain, producing the alert feeling that caffeine drinkers crave.
Soon after you drink (or eat) something containing caffeine, it’s absorbed through the small intestine and dissolved into the bloodstream. Because the chemical is both water- and fat-soluble (meaning that it can dissolve in water-based solutions—think blood—as well as fat-based substances, such as our cell membranes), it’s able to penetrate the blood-brain barrier and enter the brain.
Structurally, caffeine closely resembles a molecule that’s naturally present in our brain, called adenosine (which is a byproduct of many cellular processes, including cellular respiration)—so much so, in fact, that caffeine can fit neatly into our brain cells’ receptors for adenosine, effectively blocking them off. Normally, the adenosine produced over time locks into these receptors and produces a feeling of tiredness.

Caffeine structurally resembles adenosine enough for it to fit into the brain’s adenosine receptors. Image via Wikimedia Commons

When caffeine molecules are blocking those receptors, they prevent this from occurring, thereby generating a sense of alertness and energy for a few hours. Additionally, some of the brain’s own natural stimulants (such as dopamine) work more effectively when the adenosine receptors are blocked, and all the surplus adenosine floating around in the brain cues the adrenal glands to secrete adrenaline, another stimulant.
For this reason, caffeine isn’t technically a stimulant on its own, says Stephen R. Braun, the author or Buzzed: the Science and Lore of Caffeine and Alcohol, but a stimulant enabler: a substance that lets our natural stimulants run wild. Ingesting caffeine, he writes, is akin to “putting a block of wood under one of the brain’s primary brake pedals.” This block stays in place for anywhere from four to six hours, depending on the person’s age, size and other factors, until the caffeine is eventually metabolized by the body.

In people who take advantage of this process on a daily basis (i.e. coffee/tea, soda or energy drink addicts), the brain’s chemistry and physical characteristics actually change over time as a result. The most notable change is that brain cells grow more adenosine receptors, which is the brain’s attempt to maintain equilibrium in the face of a constant onslaught of caffeine, with its adenosine receptors so regularly plugged (studies indicate that the brain also responds by decreasing the number of receptors for norepinephrine, a stimulant). This explains why regular coffee drinkers build up a tolerance over time—because you have more adenosine receptors, it takes more caffeine to block a significant proportion of them and achieve the desired effect.

This also explains why suddenly giving up caffeine entirely can trigger a range of withdrawal effects. The underlying chemistry is complex and not fully understood, but the principle is that your brain is used to operating in one set of conditions (with an artificially-inflated number of adenosine receptors, and a decreased number of norepinephrine receptors) that depend upon regular ingestion of caffeine. Suddenly, without the drug, the altered brain chemistry causes all sorts of problems, including the dreaded caffeine withdrawal headache.

The good news is that, compared to many drug addictions, the effects are relatively short-term. To kick the thing, you only need to get through about 7-12 days of symptoms without drinking any caffeine. During that period, your brain will naturally decrease the number of adenosine receptors on each cell, responding to the sudden lack of caffeine ingestion. If you can make it that long without a cup of joe or a spot of tea, the levels of adenosine receptors in your brain reset to their baseline levels, and your addiction will be broken

Easy ways to add fruits and vegetables to dinner

Have a salad with dinner most days. Stock your salad with dark green leafy lettuce and toss in petite peas, tomatoes, onions, celery, carrots, and peppers. As an added benefit, starting meals with a salad can help you consume fewer calories at the meal, as long as the salad is no more than 100 calories. A healthful salad consists of about 3 cups of dark green lettuce, 1⁄2 cup carrots, a tomato, 1⁄4 cucumber, and 1 1⁄2 tablespoons of low-calorie dressing.

Choose fruit — fresh or frozen, stewed or baked — for dessert. It all counts toward your daily produce quota. Dried fruits are healthy but high in calories, so eat them sparingly

Roast vegetables. Roasting is a great way to let the deep, rich flavors of vegetables shine through. Bake cut vegetables at 375° F for 20 to 25 minutes or until they’re lightly browned. You can roast any vegetable — from mushrooms, onions, eggplant, and zucchini to tomatoes, broccoli, and carrots — so don’t limit yourself. Enjoy roasted veggies as a side dish or toss them into pasta dishes and other recipes.

Detox Superfoods

Detox is a natural, ongoing process of neutralizing and eliminating dietary and environmental toxins from the body. Certain foods can support, or even speed the process, by providing vitamins, antioxidants, minerals, essential fatty acids, fiber and other needed nutrients.

Pomegranate
Give yourself a serious antioxidant boost! Pomegranates are loaded with anthocyanins, a type of antioxidant that gives the seeds their deep, red color. It’s possible that anthocyanins may protect against DNA damage and inflammation and reduce the risk of heart disease, allergies, cancer, and diabetes. Preliminary research indicates that they may also help to slow skin aging by reducing the weakening of skin’s collagen and elastin fibers.

Arugula

A culinary staple in Mediterranean cooking, arugula is a type of cruciferous vegetable (like broccoli, kale, and watercress) that contain a number of compounds that aid in detoxification, such as sulforaphane and indole-3-carbinol. Arugula is also packed with vitamins and minerals such as vitamin K, vitamin C, magnesium and folate and the phytochemicals lutein and zeaxanthin, which may protect against age-related macular degeneration and cataracts.

Garlic

A detox favorite, garlic contains sulfur-containing compounds that may fight harmful bacteria and yeast in the intestines and boost the body’s ability to detox by increasing production of glutathione, needed for the elimination of certain toxins. The sulfur compounds, called allicin, are broken down in the body to allyl sulfides, which may guard against heart disease, certain types of cancer, arthritis and diabetes

Seaweed

A dietary staple in many Asian countries, seaweeds-such as dulse, kelp, nori, wakame, and agar- are becoming popular with good reason. They are packed with minerals such as iodine, which aids in the production of thyroid hormone and regulates our metabolism, calcium, magnesium and potassium. The high mineral content can help to flush toxins from the body. Certain seaweeds, such as arame and hijiki have plenty of soluble fiber, which also promotes detoxification.

Lemon

One of the most potent detox foods around, lemons are packed with vitamin C and are thought to help restore the alkaline-acid balance of the body, enabling us to more effectively remove dietary and environmental toxins.

Apples

Apples are high in insoluble fiber and the soluble fiber pectin, which soaks up toxins and waste and sweeps them through the intestines. They are low-glycemic, which means that they are absorbed slowly with a gradual rise in blood sugar and insulin. Apples contain glucaric acid, which helps the body get rid of estrogen-like chemicals and heavy metals.

Cabbage

One of the more affordable detox foods, cabbage has cleansing properties due to their high content of glucosinolates, sulfur-containing compounds that are converted into active forms isothiocyanates and indoles. Isothiocyanates may prevent cancer by promoting the elimination of potential carcinogens from the body. It is also high in vitamin K and vitamin C and ½ cup has only 11 calories.

Quinoa

Quinoa has been cultivated in South America for over 5000 years. Wheat-free and gluten-free, quinoa is a popular detox food and technically the seed of a plant (related to beets and spinach) rather than a whole grain. A protein powerhouse - one half cup of cooked quinoa has 3 grams of protein - quinoa has 50 percent more protein than grains and contains all nine essential amino acids, making it a complete protein similar to meat and other animal foods and a great food for people who follow a vegetarian or vegan diet.

Quinoa is also low on the glycemic index, meaning that it causes a gradual rise in blood sugar and insulin, and it is high in the amino acid lysine, which is involved in tissue repair.  

Wheatgrass

A popular ingredient at juice bars, wheatgrass is thought to have potent detoxifying abilities, being packed with chlorophyll, amino acids, vitamins, minerals, and enzymes.

Almonds

Almonds are actually fruit because they're the seeds of a fruit that is a close relative to the plum and peach. They're a detox essential because most detox diets don't include cow's milk, and almond milk is one of the best-tasting, most readily available plant-based alternatives. Almond milk can be made at home, or you can find it at many grocery stores and health food stores.

Almonds are also fantastic because they have a high vitamin E content (one ounce has 35% of the daily recommended intake), fiber (one ounce has 3 grams), vegetable protein (one ounce has 6 grams), and monounsaturated fats (almonds are 51% monounsaturated fat). They're also rich in magnesium, phosphorus, calcium, iron, folate, and phytochemicals, all of which may help prevent chronic diseases

Avocados

During the low-fat diet craze of the 1980s and 90s , avocados became an off-limits food because of their fat content. While they do contain a fair amount of fat, they are high in heart-healthy monounsaturated fat which won’t interfere with the balance of omega-3 to -6 fatty acids in the diet.

Fat is essential during a detox diet, because it promotes the release of bile from the gallbladder, allowing for the elimination of toxins from the body and the absorption of fat-soluble vitamins including vitamin A, vitamin D, vitamin E and vitamin K. Besides providing a desirable fat, avocados also contain vitamin E, folate, vitamin B5 and potassium. One half-cup of avocado has a whopping 8 grams of dietary fiber.

Blueberries

A true detox superfood, blueberries are packed with fiber and vitamin C, are low in calories (1/2 cup has 44 calories), and are one consistently ranked at the top when it comes to antioxidant capacity.

Blueberries get their blue color from antioxidant pigments called anthocyanins, which help protect cells from free radical damage, enhance glutathione production, and guard against heart disease, cataracts, glaucoma, peptic ulcers, Alzheimer’s disease, allergies, diabetes and certain cancers. Anthocyanins may also slow aging by reducing the breakdown of collagen and strengthening blood vessels and capillaries.

Ginger

No list of detox foods would be complete without ginger. A natural anti-inflammatory food, ginger also helps to ease nausea, improve digestion, and promote detoxification by speeding the movement of food through the intestines, thanks to compounds called gingerols and shogaols.

Cauliflower

Don’t let its lack of color fool you. Cauliflower makes our list of top detox foods because it is a cruciferous vegetable (a family that includes broccoli, cabbage and bok choy) that is high in phytochemicals called glucosinolates. These chemicals are broken down in the intestines to isothiocynates and indole-3-carbinol, compounds which regulate the body’s detoxification enzymes and protect against cancer

Parsley

Known primarily as a culinary herb, parsley contains vitamin C, chlorophyll, beta-carotene, vitamin K and folate, which are all needed by the body for detox. Parsley also raises glutathione levels and may guard against liver dysfunction due to insulin resistance.

Beets

Packed with potassium, folate, fiber and antioxidants, beets are a star detox food. Beets also contain betaine, a compound that has been found to lower the levels of several inflammatory markers, protect against liver damage, and help the liver process fats. It also contains the beautiful reddish-purple antioxidant pigment betacyanin, which is responsible for a host of health benefits and may provide anti-inflammatory, antioxidant, and detoxification support (notably supporting glutathione-dependent phase 2 detoxification). Beets are low in calories – 1/2 cup of beets contains 40 calories.

Green Tea

If you are trying to cut back on your coffee intake, green tea is a good substitute. It has some caffeine (about 15 to 40 mg per cup), but also contains epigallocatechin-3-gallate (EGCG). A potent antioxidant, EGCG may protect the liver against damage from toxins, prevent the oxidation of LDL cholesterol, and may help prevent heart disease and certain cancers.

Flaxseeds

Flaxseeds contain alpha-linolenic acid, a heart-healthy omega-3 fatty acid that appears to improve how the body uses insulin, the hormone that clears sugar from the bloodstream. They also have soluble and insoluble fiber, which helps the body’s detoxification by promoting bowel regularity and helping the body to eliminate excess toxins, cholesterol and waste. Flaxseeds are also an excellent source of manganese.

Fennel

Fennel, a root vegetable with a licorice flavor, is low in calories and is a good source of folate, potassium and antioxidants such as anethole, a phytochemical which has been found to reduce inflammation. It is also mildly diuretic, which may help with the removal of toxic substances from the body Half a cup of raw fennel has only 14 calories.

Detox Foods to Eat

A detox diet is short, focused diet program focused on eliminating environmental and dietary toxins from your system. Although there are many types of detox diets, the foods that are allowed are often quite similar, unless it is a juice fast.

Fruits

fresh or frozen fruits

unsweetened, natural juice

dried fruit - unsweetened, in limited amounts, such as cranberries, dates, raisins, goji berries

Vegetables

• Vegetables thought to be particularly good detox foods include broccoli, cauliflower, broccoli sprouts, onions, garlic, artichokes, beets, and dark leafy greens such as kale, collard greens, and swiss chard
• sea vegetables, including kelp, nori sheets, wakame
• corn - avoid corn as it is acid-forming
• note: some people are sensitive to the nightshade family of vegetables, which includes tomatoes, bell peppers, eggplants, and potatoes, and may wish to avoid them

Grains and Starches

• rice, especially brown rice
• quinoa
• buckwheat
• millet
• amaranth
• wild rice
• oats
• whole grains are preferred, but products made from the above may be allowed, such as brown rice pasta, pure buckwheat noodles, rice crackers, and bread

Beans and Legumes

• split yellow and green peas
• lentils
• adzuki beans

Nuts and Seeds

• almonds
• cashews
• walnuts
• sunflower seeds
• pumpkin seeds
• sesame seeds
• chia seeds
• hemp seeds, hemp nuts
• coconut, especially young coconuts
• tahini
• nut and butters made only with allowed ingredients
• peanuts and peanut butter - usually not recommended

Choose unsalted, raw nuts and seeds.

Oils

• cold-pressed, extra-virgin olive oil
• hemp oil
• flax oil
• chia oil
• almond oil
• avocado oil
• coconut oil
• safflower, sesame, and sunflower oils in limited amounts (due to omega-6 fatty acids)

Beverages

"milks" made from allowed foods, such as rice milk, almond milk, hemp milk

coconut milk - except canned coconut milk

water

herbal teas

green tea

lemon water

unsweetened juice made from allowed fruits and vegetables

mineral or seltzer water - in limited amounts

Exercise Boosts Health From the Start

One step in front of the other—that’s all it takes to start getting fit. Even so, for people who don’t exercise, that first step can seem like a giant leap. Only 1 out of 5 people in the United States exercises for the recommended 150 minutes per week, according to a recent report by the Centers for Disease Control and Prevention.

Looking for motivation? Try focusing on exercise’s immediate benefits instead of taking the long view. Research shows that every time you exercise, your body gets a quick health boost. This goes double for people with diabetes because of extra blood glucose benefits. “We are realizing more and more how exercise is like a medicine,” says Barry Braun, PhD, associate professor of kinesiology at the University of Massachusetts–Amherst. “You take it in a dose, it has an effect, and, over time, it wears off. Then you have to take it again.”

Prescribing Sweat
Exercise is a particularly effective medication for people with diabetes, and here’s the nice thing: Its benefits are the same whether you are a marathon runner or a couch potato. “It doesn’t matter if you are trained or untrained,” says Sheri Colberg-Ochs, PhD, professor of exercise science at Old Dominion University in Norfolk, Va. “The reason it’s helpful for everyone … is that you have two mechanisms to get blood glucose out of your bloodstream.” And exercise revs up them both.

The first route to lower blood glucose levels is via insulin, a hormone that ushers glucose from the blood into the body’s cells, where it can be processed into energy. But people with type 2 diabetes are insulin resistant, meaning their cells are less responsive to insulin. Exercise temporarily lessens the cells’ resistance. “If you exercise for 30 minutes, then you have improved insulin action from two to 72 hours after,” says Colberg-Ochs.

Exercise also activates a completely insulin-independent route into the muscles. During exercise, a little door opens up to the muscles so that they directly absorb glucose from the blood.  

Another exercise benefit for everyone regardless of fitness level, according to Colberg-Ochs, is that it creates space in the muscles to store glucose coming into the body from what you eat. Your muscles can spin glucose into a large molecule called glycogen, which stores the sugar until it’s needed. But there’s only room in each muscle cell for a fixed amount of glycogen. “If you think of the glycogen as your storage tank for carbs, when glucose comes in, it can go in the storage tank,” says Colberg-Ochs. Yet that’s only true if there is enough space in the muscle cells to store incoming glucose. “If you don’t [exercise], the tank is always full.” Full muscles force the body to send that homeless glucose to the liver, which turns it into fat for long-term storage. Too much fat in the liver is harmful.

Just Beat It
The benefits of exercise don’t stop with blood glucose. The heart gets into the action right away, too, thanks to a boost in beats per minute. Blood pressure decreases after exercise because the heart pumps blood harder through the circulatory system. “Increased blood flow makes blood vessels more compliant and elastic, which allows them to handle more pressure,” says Braun. “You want them to be as flexible as possible.”

Exercise’s mood enhancements can be felt immediately as well. “I don’t know how to quantify this, but everyone is a nicer person after they exercise,” says Braun. This lifting of mood may be an especially attractive incentive for people with diabetes, who are at increased risk of developing depression. “Exercise is an effective treatment,” says Colberg-Ochs. “It releases brain hormones, such as dopamine, and the other ‘feel good, be happy’ kind of hormones that you will start feeling right away.” These are the same pleasure hormones that are released when eating sugar, salt, and fat. So for people who are trying to eat healthfully, exercise “is a good way to replace the hormones,” she says, because a walk can make you feel just as good as a bowl of ice cream can. The better mood can last for hours.

What about being stronger and slimmer? That takes time, and evidence suggests that exercise is better at helping people maintain weight than drop pounds. Even so, muscle improvements from strength training can happen surprisingly fast, says Braun: “People feel the difference very quickly. The first two, three, or four times you do it, you see a big change.
”

Health Benefits of Black Pepper

Black pepper can add a lot more to your food than just flavour.  Apart from the piperine, black pepper also contains Vitamin C, Vitamin A, flavonoids, carotenes and other anti-oxidants that help remove harmful free radicals and protect the body from cancers and diseases. Other studies have suggested its efficacy in stalling the progression of skin cancers and bowel and colon cancer as well. Add a teaspoon of pepper powder to your food once a day. It is better that you eat freshly ground pepper rather than adding it to a dish while cooking.

Helps in digestion: The piperine content of black pepper makes it a great digestive. It stimulates the taste buds to signal the stomach to produce more hydrochloric acid. This acid is essential to digest proteins and other foods in the stomach, which when left undigested cause flatulence, indigestion, diarrhoea, constipation and acidity. The excess hydrochloric acid secreted helps in preventing these conditions. To aid in digestion, add a tablespoon (depending on the number of servings being prepared) of freshly ground pepper powder to your meal, while cooking. It will add to the flavour of the dish and keep your stomach healthy.

Helps you lose weight: Black  pepper is great in aiding the proper assimilation (extraction of all the nutrients) of food. Moreover, its outer layer which contains potent phytonutrients stimulates the breakdown of fat cells. It also promotes sweating and urination and is a great way to get rid of excess water and toxins from the body.  All these activities collectively help in weight loss. For effective weight loss, just sprinkle pepper over your food. Do not eat too much of the spice, it can cause severe side effects.

Relieves gas: Known for its carminative properties (a substance that prevents the formation of gas) black pepper is great to relieve discomfort caused due to flatulence and colicky pain. Adding pepper to your meals instead of chili powder will help relieve flatulence. Black pepper increases the cognitive function of the brain and helps beat depression. It was also found that pepper eaten on a regular basis helps the brain function properly. Add it to your daily meal, or eat it as seasoning on a salad. Pepper in any form can help make you smarter and less depressed.

How Exercise Can Help Us Learn

Over the past decade, in study after study in animals and people, exercise has been shown to improve the ability to learn and remember. But the specifics of that process have remained hazy. Is it better to exercise before you learn something new? What about during? And should the exercise be vigorous or gentle?

Two new studies helpfully tackle those questions, with each reaching the conclusion that the timing and intensity of even a single bout of exercise can definitely affect your ability to remember — though not always beneficially.

To reach that conclusion, scientists conducting the larger and more ambitious of the new studies, published in May in PLoS One, first recruited 81 healthy young women who were native German speakers and randomly divided them into three groups. Each group wore headphones and listened for 30 minutes to lists of paired words, one a common German noun and the other its Polish equivalent. The women were asked to memorize the unfamiliar word.

But they heard the words under quite different circumstances. One group listened after sitting quietly for 30 minutes. A second group rode a stationary bicycle at a gentle pace for 30 minutes and then sat down and donned the headphones. And the third group rode a bicycle at a mild intensity for 30 minutes while wearing the headphones and listening to the new words.

Two days later, the women completed tests of their new vocabulary. Everyone could recall some new words. But the women who had gently ridden a bicycle while hearing the new words — who had exercised lightly during the process of creating new memories —performed best. They had the most robust recall of the new information, significantly better than the group that had sat quietly and better than the group that had exercised before learning. Those women performed only slightly better than the women who had not exercised at all.

That result contrasts tellingly with the findings of another new study of memory formation and exercise, presented in May at the annual meetingof the American College of Sports Medicine in Indianapolis. During this study, 11 female collegians read a dense chapter from a college textbook on two occasions: once while sitting quietly and, on a separate day, while exercising vigorously on an elliptical machine for 30 minutes. Immediately after each session, the students were tested on the material they’d just read. They were then retested the next day.

In this study, exercise did not help the women’s memories, at least in the short term. Their test scores were actually worse on the memory test conducted immediately after they’d exercised while reading compared with their scores taken soon after they’d been sitting quietly and studying.

But the recall gap disappeared the next day, when the women were retested. At that point, there were no differences in their scores, whether they’d vigorously exercised while learning the new material or not.

The message of these studies would seem to be that exercise timing and intensity interact to affect memory formation, said Maren Schmidt-Kassow, a professor at the Institute of Medical Psychology at Goethe University in Frankfurt, Germany, who led the study of gentle bicycling and memory. Exercising during learning was, in her study, significantly more effective than exercising beforehand or not exercising at all.

But that beneficial impact probably depended on the mildness of the workout, she said. Light-intensity exercise will elicit low but noticeable levels of physiological arousal, she said, which, in turn, presumably help to prime the brain for the intake of new information and the encoding of that information into memories.

If the exercise is more vigorous, however, it may overstimulate the body and brain, she said, monopolizing more of the brain’s attentional resources and leaving fewer for the creation of robust memories.

This theory also helps to explain why, in both studies, memory recall was best a day or two after exercise, by which time, Dr. Schmidt-Kassow said, physiological arousal would have dissipated.

Of course, the mysteries of human memory remain, by and large, mysteries. These new studies don’t explain how, for instance, at a molecular level, exercise affects the creation of individual memories. It is likely that, as part of the arousal process, exercise stimulates the release of certain chemicals in the brain that affect memory formation, Dr. Schmidt-Kassow said. But that idea has yet to be proven, although she and many other scientists have applicable studies underway.

For now, though, there is some practical takeaway from the current studies, said Walter Bixby, an associate professor at Elon University in North Carolina, who oversaw the study of vigorous exercise and reading. “If you have an exam” or other activity that involves memorizing and recalling information “in a few hours, you would probably be better off sitting quietly and studying,” he says. “However, if the exam is the next day, it won’t hurt you to study while exercising.” And if your workout is gentle, it could even help.

How Sleep Loss Adds to Weight Gain

Losing sleep tends to make people eat more and gain weight, and now a new study suggests that one reason may be the impact that sleep deprivation has on the brain.

The research showed that depriving people of sleep for one night created pronounced changes in the way their brains responded to high-calorie junk foods. On days when the subjects had not had proper sleep, fattening foods like potato chips and sweets stimulated stronger responses in a part of the brain that helps govern the motivation to eat. But at the same time, the subjects experienced a sharp reduction in activity in the frontal cortex, a higher-level part of the brain where consequences are weighed and rational decisions are made.

The findings suggested that one unfortunate result of sleep loss is this “double hit” in brain activity, said Matthew P. Walker, an author of the study and a professor of psychology and neuroscience at the University of California, Berkeley. A sleepy brain appears to not only respond more strongly to junk food, but also has less ability to rein that impulse in.

Some experts have theorized that in a sleep-deprived state, people eat more food simply to make up for all the calories they expend as they burn the midnight oil. But the new study showed that the changes in brain activity were evident even when the subjects were fed extra food and not experiencing any increased sensations in hunger.

“Their hunger was no different when they were sleep deprived and when they had a normal night of sleep,” Dr. Walker said. “That’s important because it suggests that the changes we’re seeing are caused by sleep deprivation itself, rather than simply being perhaps more metabolically impaired when you’re sleep deprived.”

The relationship between sleep loss and weight gain is a strong one, borne out in a variety of studies over the years. Large population studies show that both adults and children are more likely to be overweight and obese the less they sleep at night. In smaller, controlled studies, scientists find that when people are allowed to sleep eight hours one night and then half that amount on another, they end up eating more on the days when they’ve had less sleep. One pivotal study at the University of Colorado in March showed that losing just a few hours of sleep a few nights in a row caused people to pack on an average of about two pounds.

Other studies have found that the underlying effects of sleep deprivation on the body can in many ways be pronounced. The stress hormone cortisol climbs and markers of inflammation rise. Hormones that stimulate appetite increase, while hormones that blunt it drop. People become less sensitive to insulin, raising their risk of Type 2 diabetes.

But until now, few if any studies have looked at precisely what goes on in the brain when people are starved of sleep and then faced with food decisions.

In the new study, which was published in the journal Nature Communications, Dr. Walker and his colleagues recruited 23 healthy men and women and assigned them to two different regimes, each separated by about a week. On one occasion, the subjects came into the lab and got a normal night of rest – roughly eight hours – before waking up to a small breakfast of toast and strawberry jam.

The subjects then looked at 80 pictures of a variety of foods and were asked to rate how strongly they wanted them while an imaging machine measured brain activity. The subjects were told that after looking through the pictures, they would receive one of the foods that they rated the highest.

On another occasion, the subjects followed the same routine, but this time, instead of sleeping, they stayed awake through the night. They were also given snacks – like apples and peanut butter crackers – to offset any extra calories that they burned while staying awake.

The research showed that when the subjects were bleary-eyed and sleep-deprived, they strongly preferred the food choices that were highest in calories, like desserts, chocolate and potato chips. The sleepier they felt, the more they wanted the calorie-rich foods. In fact, the foods they requested when they were sleep deprived added up to about 600 calories more than the foods that they wanted when they were well rested.

At the same time, brain scans showed that on the morning after the subjects’ sleepless night, the heavily caloric foods produced intense activity in an almond-shaped structure called the amygdala, which helps regulate basic emotions as well as our desires for things like food and experiences. That was accompanied by sharply reduced responses in cortical areas of the frontal lobe that regulate decision-making, providing top down control of the amygdala and other primitive brain structures.

One expert who was not involved in the new study, Dr. Kenneth P. Wright Jr., called the findings exciting and said that they help explain why people make poor dietary choices and eat much more than they need to when fatigued.

“There’s something that changes in our brain when we’re sleepy that’s irrespective of how much energy we need,” said Dr. Wright, the director of the sleep and chronobiology lab at the University of Colorado at Boulder. “The brain wants more even when the energy need has been fulfilled.”

But why would a lack of sleep disrupt the brain response to food?

Dr. Walker said he suspected that one factor that plays a role is a substance called adenosine, a metabolic byproduct that disrupts neural function and promotes sleepiness as it accumulates in the brain. One of the ways that caffeine stimulates wakefulness is by blocking adenosine. Adenosine is also cleared from the system when we sleep.

Without enough rest, adenosine builds up and may start to degrade communication between networks in the brain, Dr. Walker said. Getting sleep may be the equivalent of rebooting the brain.

“I think you have about 16 hours of optimal functioning before the brain needs to go offline and sleep,” he said. “If you go beyond these 16 hours into the realm of sleep deprivation, then those brain networks start to break down and become dysfunctional.”

Dr. Walker said it was increasingly clear from the medical literature that there is not a single tissue in the body that is not beneficially affected by sleep.

“It’s the single most effective thing people can do every day to reset their brain and body health,” he said.