Brilliance crackles in the pages of Marion Nestle and Malden Nesheim's "Why Calories Count." The authors, who are professors of food science (and Nestle also in sociology) at NYU and Cornell respectively, deliver a plain-English presentation for non-scientists. They unpack what is a calorie in physical terms, and how calories relate to food from different sources - carbohydrate, protein, fat, and alcohol. They survey alternative theories and folk notions about what makes weight loss or weight gain happen. Contrary to "lowfat" and "low-carb" diet advocates and food marketers, Nestle and Nesheim reaffirm, loudly and clearly, a long-held scientific proposition: that calorie balancing, not food composition, overwhelmingly determines weight gain, weight loss, and weight steadiness.
That makes a good book right there. But "Why Calories Count" does a whole lot more. In just a couple-hundred pages of prose that is colorful, reasonable, and easy-to-read, Nestle and Nesheim unfurl a scientific detective story about food and society. They cut through a lot of dieting mythology and food marketers' hype. They expose troubling trends in eating as a matter of public health. And they reveal clear-eyed solutions to better eating that are available to individuals.
Standing on sound science, the book stages a drama about food and society in America against a 125-year historical backdrop. The protagonist is the American food consumer - sometimes overeater and sometimes dieter - who is driven by personal taste, biology, and good intentions at times. The cast of characters includes: food scientists, professional nutritionists, and diet marketers; farmers, agribusiness, and food marketers; restaurants; and food policymakers in federal, state, and local governments.
One problem the authors clear up in this book is a lack of public understanding for what a calorie is. Early in the story, the star is Wilbur Atwater, a 19th-century chemist and public health advocate whose work on food and calories stands almost unaltered today, more than 100 years after his last days in the laboratory. The book's history-of-science stories about food studies, including the technology used to understand calories over the years, makes the idea of "calories" - in food and in the body - something you really can picture. One can almost imagine building a lab-quality "calorimeter" in a home or restaurant kitchen after reading this book. Not that you'd want to, though. And not that you'd need to. On the question of how to estimate calories, the authors emphasize that the basic estimates are mostly good enough, using published lists and online databases, along with a food scale and measuring cups.
The one place you'll want to be skeptical of published calorie counts is on restaurant menus that state calorie estimates. Federal and local laws give restaurants a lot of leeway on calorie postings. Not surprisingly, they tend to lowball their estimates. Sometimes the real counts are double what the menu says! (p. 215). This makes it tricky when eating out because it's very hard to estimate calories without knowing what all is in the food, and in what proportions. The details of restaurant food ingredients and measurements belong to the restaurant owner and the kitchen staff, not the patron who eats the meal. Even professional nutritionists come to grief when they try to estimate the calories in restaurant meals: they typically underestimate by about 30%. (p. 187) Add the fact that Americans of all ages are eating out much more than ever before, and you've got a public health challenge that Nestle and Nesheim tackle head-on in this book. They blame our "eat more" environment.
On the subject of obesity and public health, the authors have a lot to say. Obesity in America and worldwide has risen sharply in recent decades. From 1975 to 2008, the rate of obesity in America jumped from 13% to 34%. (p. 141) One group of experts at Harvard University predicts the rate of obesity in the U.S. will balloon to 42%.
Nestle and Nesheim summarize the health risks of obesity: "Concerns about obesity would not be so pronounced if this condition were simply a matter of appearance. Excessive calorie intake does not always cause disease, but when it does the problems can be serious. And the list of such problems is long, including such leading causes of death and disability as coronary heart disease, high blood pressure, type 2 diabetes, certain cancers (endometrial, breast, colon), stroke, liver, and gallbladder disease, sleep apnea and respiratory problems, osteoarthritis, and gynecological problems such as abnormal menses and infertility. (p. 140-41)
How does a person slim down? This is not a "diet book" per se, but it certainly can help any dieter or mindful eater. The authors recognize that many readers are concerned to identify which diets work, which don't, and why. Nestle's and Nesheim's answer to that is strewn throughout the book and highlighted in chapter 20, entitled, "Do Some Kinds of Diets Work Better Than Others?" Their answer is that while some diets are more nourishing and advisable than others, *any* diet in controlled portions can bring about weight loss if the dieter expends more calories than he or she eats. Food professionals and the public have heard this sort of message time and again for more than a hundred years, beginning with Wilbur Atwater. The key is calorie balancing and creating a deficit to lose weight. But for reasons that Nestle and Nesheim unravel, calorie balancing is very difficult for most people to manage directly. Many diet prescriptions may help dieters achieve calorie regulation through indirect means.
From the standpoint of sound nutrition and calorie balancing success, the authors endorse good-old "moderation" for those who are able to get by on that maxim. And they look with qualified favor on low-sugar diet strategies (p. 170-72). For some people, a simple rule of moderation is sufficient to regulate calories and balance one's weight appropriately. The authors say they, personally, "are lucky enough to be able to stop when we've had enough. If you can't do that - and we know many people who can't - choosing foods with a low glycemic index (those low in rapidly absorbable sugars and starches) is always a good idea, as is setting some limits on the size and frequency of desserts and sugary drinks. Everything is fine in moderation. But if you can't do moderation, you had best figure out some limits you can live with." (p. 222)
If scientists have known for so long that calorie balancing is the biological mechanism underlying weight management, why don't people just do it? Successful food marketers and restauranteurs know part of the answer to that. (p. 184-5) "Why Calories Count" cites Brian Wansink's excellent book on food and marketing psychology,
Mindless Eating: Why We Eat More Than We Think (2006). For one, Americans have come to eat out more often, and expect larger servings. At home too, larger portions of everything has become the norm. Food ubiquity and eating frequency have increased, and food industry marketing has intensified the allure of the call to "eat more." Research shows that the food industry has turned even health-seeking eaters into gluttons through the "health halo" effect. This is a paradox where people who choose snack foods with healthy-sounding labels (low-calorie or lowfat) wind up eating larger portions - so much more that they wind up eating more calories in the end! Everywhere, outside the home and inside, larger portions prevail.
Faced with this, human biology is ill-suited. The evolutionary process of natural selection, having taken place over a ga-zillion years, has not prepared us for this very recent environment. Nestle and Nesheim make this point throughout the book: "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. The result is that it is much easier for you and everyone else to overeat than to stop eating when you are no longer hungry." (p. 78)
Elsewhere they put a still heavier point on social drivers to overeating that overcome biology in modern life: "In food environments that aggressively promote overconsumption of high-calorie foods, the `eat more' signals overpower those that promote satiety. In such environments, matters largely beyond personal control - the presence of other people, the location of meals, how often meals appear, how large food portions might be, how tasty the foods are, and how they are advertised - are remarkably effective at overcoming physiological regulatory mechanisms." (108-9).
Once someone has put on extra pounds, biology works against the dieter's best intentions. "Some people can handle the temptations of an `eat more' food environment and remain relatively thin, but many others cannot and find it all too easy to consume more calories than they need." (p. 172)
The emphasis here on biology is interesting, relevant, and clarifying. At the same time, I take Nestle and Nesheim to be giving short shrift to the *psychology* of overeating. They say you can't change your biology, and that may be true; but you can re-learn new habits and re-arrange some aspects of your eating environment - especially at home. Biology and psychology are related and do overlap, but they're not the same thing. Different mechanisms are at work in natural selection and learned habits. The resulting solutions may be different.
Barbara Rolls, creator of the Volumetrics diet, is cited in "Why Calories Count" (p. 220) as one example of a popular diet that teaches people to "eat less.
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