Calories Are Everywhere, Yet Hard to Track

Americans are having a passionate love affair with something they cannot see, hear, feel, touch or taste. That something is calories, billions upon billions of which are consumed every day, often unwittingly, at and between meals.
Certainly calories are talked about constantly, and information about them appears with increasing frequency on food labels, menus, recipes and Web sites. But few people understand what they are and how they work — especially how they have worked to create a population in which 64 percent of adults and a third of children are overweight or obese, or how they thwart the efforts of so many people to shed those unwanted pounds and keep them off once and for all.

Enter two experts: Marion Nestle, a professor of nutrition, food studies and public health at New York University; and Malden Nesheim, professor emeritus of nutritional sciences at Cornell University. Together they have written a new book, “Why Calories Count: From Science to Politics,” to be published April 1, which explains what calories are, where they come from, how different sources affect the body, and why it is so easy to consume more of them than most people need to achieve and maintain a healthy weight.

“The human body does a superb job of making sure that it gets enough calories to meet biological needs but is much less effective at knowing when calories are in excess,” they wrote. “The result is that it is much easier to overeat than to stop eating when you are no longer hungry.”

Out of Control

People living in affluent societies today swim in a sea of redundant calories. Food is everywhere, and it is relatively inexpensive, accounting for about 10 percent of Americans’ disposable income on average, Dr. Nestle said in an interview.

“When did it become O.K. to eat in bookstores?” she asked. “Or in Staples? Bed, Bath and Beyond, or drugstores?”

Portion sizes — especially restaurant portions — have mushroomed out of control, she noted.

“People who pay attention to calorie labels on menus are shocked, for example, to discover that a single cookie contains 700 calories,” Dr. Nestle said. “You may want that cookie, but then you can’t eat anything else. Cookies didn’t used to be this big.”

Nor were bagels, now 500 or 600 calories each, or sodas, available in sizes as large as 64 ounces.

The shock extends to those supposedly in the know. Recently Lisa Young, a colleague of Dr. Nestle at New York University, asked the students in her nutrition class how many calories were in a Double Gulp, a 64-ounce soda available at 7-Eleven convenience stores. She’d already told them that an eight-ounce soda has 100 calories, but the students guessed a Double Gulp contains less than 400 calories.

When Dr. Young asked why their estimate was off by 100 percent, they simply said, “800 calories — that can’t be!”

People who do check calorie information on nutrition labels often fail to note the size of the serving it applies to. A serving of ice cream is just a half-cup, a burger is three ounces, and uncooked pasta is merely two ounces. A pound of pasta, therefore, should feed eight people, not two or four; two ounces per serving is about what Italians consume as a first course.

A typical American restaurant meal is more like dinner for two. Dr. Nestle said restaurants have resisted her suggestion to serve half the amount of food for about a third the price. She recently found at one New York restaurant that a “personal-size pizza” contained 2,100 calories, the amount the average woman needs in a day.

“And that didn’t include the soda and dessert,” she said. “Unless you’re in the kitchen watching what the chef is doing, you have no idea how many calories are being packed into a given dish.”

Health claims for foods are another seductive factor encouraging overconsumption, Dr. Nestle said. She’s found that words imparting “a health aura — like ‘organic’ or ‘low-fat’ or ‘heart-healthy’ — can prompt people to forget about calories.”

Ending Excess

The human body has a very complex and redundant system to make sure the brain gets the sugar calories it needs to function, Dr. Nestle and Dr. Nesheim explain in their book. At least 100 different hormones, enzymes and other chemicals — with more likely to be discovered — act to regulate appetite and to assure that people eat enough to maintain brain function.

But it is these very systems that go into overdrive during starvation (translation: a reduced-calorie diet), making it so difficult for people to lose weight.

As seductive as the current food environment is, it is still easier not to gain excess weight in the first place. Most people seriously underestimate how much they eat. For example, participants in the Nurses’ Health Study report consuming 1,600 calories a day, but their body mass index on average is 26 or higher — well into the overweight range and supported by many more calories than the women seem to think they are eating.

“I don’t count calories, and I don’t recommend counting calories,” Dr. Nestle said. “I recommend eating food. You have to pay attention to eating better and in moderation: plenty of fruits and vegetables, lean meats, and whole grains in reasonable portions, and not too much junk food.”

She applauded the current campaign by the New York City Department of Health and Mental Hygiene to get people to stop “pouring on the calories” by consuming fewer sugar-sweetened soft drinks.

Dr. Nestle and Dr. Nesheim also review the weight-regulating effects of different sources of calories. Is it high-fructose corn syrup that makes so many people fat? Are other carbohydrates to blame, or fat — or what?

They found scant evidence to support the popular notion that any one nutrient is responsible for our obesity, or that a low-carbohydrate diet is everyone’s secret to success.

Although a diet low in carbs and high in fats and protein may enhance satiety and curb snacking, few people seem able to refrain indefinitely from the carbohydrate-rich foods they love. The long-term effectiveness of low-carb diets for a vast majority of people who try them has yet to be assessed.

“The source of the calories may make a small difference in weight maintenance or loss, but it appears to be much less important than the ability to resist pressures to overeat calories in general,” the authors wrote.

And since most people cannot come close to estimating how many calories they consume or expend in a day, a better way to monitor intake and output, Dr. Nestle said, is to regularly check the notches on one’s belt or numbers on the scale.

“It’s much easier to lose a pound or two than 20 or 30,” she said.

Of course, the amount of calories consumed is not the only factor influencing weight. Calories expended count as well, and the more active people are, even if they are simply fidgety, the better able they are to balance intake with output.