Good Calories, Bad Calories (48 page)

Obese patients also get hungry on semi-starvation diets. If they have to restrict their calories to lose weight, then by definition they are forcing themselves to eat less than they would otherwise prefer. Their hunger is not being satisfied. As with lean subjects, their energy expenditure on a semistarvation diet also “diminishes proportionately much more than the weight,” as the Pittsburgh clinician Frank Evans reported in 1929 of his obese subjects. This same observation was reported in 1969 by George Bray, who was then at the Tufts University School of Medicine in Boston, and who entitled his article, for just this reason, “The Myth of Diet in the Management of Obesity.” “There is no investigator who has looked for this effect and failed to find it,” the British obesity researcher John Garrow wrote in 1978.

The latest reiteration of these experiments, using obese subjects, was conducted by Jules Hirsch at Rockefel er University, and the results were published in The New England Journal of Medicine in 1995. Calorie restriction in Hirsch’s experiment resulted in disproportionate reductions in energy expenditure and metabolic activity. Increasing calorie consumption resulted in disproportionate increases in metabolic activity.

Hirsch and his col eagues interpreted their observations to mean that the human body seems surprisingly intent on maintaining its weight—resisting both weight gain and weight loss—so that the obese remain obese and the lean remain lean. As Hirsch explained it, the obese individual appears to be somehow metabolical y normal in the obese state, just as Keys’s and Benedict’s young men were metabolical y normal in their lean or overweight states before their semi-starvation diets. Once Hirsch’s obese subjects took to restricting their calories, however, they experienced what he cal ed “al the physiological and psychological concomitants of starvation.” A semi-starvation diet induces precisely that—semi-starvation—whether the subject is obese or lean. “Of al the damn unsuccessful treatments,” Hirsch later said, “the treatment of weight reduction by diet for obese people just doesn’t seem to work.”

Over the course of a century, a paradox has emerged. Obesity, it has been said, is caused, with rare exceptions, by an inability to eat in moderation combined with a sedentary lifestyle. Those of us who gain excessive weight consume more calories than we expend, creating a positive caloric balance or a positive energy balance, and the difference accumulates as excessive pounds of flesh. But if this reconciles with the equal y “indisputable” notion that “eating fewer calories while increasing physical activity are the keys to control ing body weight,” as the 2005 USDA Dietary Guidelines for Americans suggest, then the problems of obesity and the obesity epidemic should be easy to solve. Those few individuals for whom obesity is a preferred condition, such as sumo wrestlers, would remain obese through their voluntary program of overeating, and the rest would create a negative energy balance, lose the excess weight, and return to leanness. The catch, as Hirsch pointed out, is that this doesn’t happen.

The documented failure of semi-starvation diets for the obese dates back at least half a century. It begins with Albert Stunkard’s analysis of the relevant research in the mid-1950s, motivated by his desire to resolve what he cal ed the “paradox” between his own failure to reduce obese patients successful y by diet at New York Hospital and “the widespread assumption that such treatment was easy and effective.” Stunkard managed to locate eight reports in the literature that al owed for an accurate assessment of whether semi-starvation diets worked. In 1959, he reported that the existing evidence confirmed his own failures: semi-starvation diets were “remarkably ineffective” as a treatment for obesity. Only 25 percent of the subjects discussed in these articles had lost as much as twenty pounds on their semi-starvation diets, “a smal weight loss for the grossly overweight persons who are the subjects of these reports.” Only 5 percent successful y lost forty pounds. As for Stunkard’s own experience with a hundred obese patients, al prescribed “balanced” diets of eight to fifteen hundred calories a day, “only 12% were able to lose 20 lb., and only 1 patient lost 40 lb….Two years after the end of treatment only two patients had maintained their weight loss.”*76

A decade later, when Stunkard was invited to discuss obesity at Richard Nixon’s White House Conference on Food, Nutrition, and Health, he had come to believe that the adverse effects caused by semi-starvation diets as a treatment for obesity often outweighed any benefits. “Attempts at weight reduction are often accompanied by anxiety and depression, at times severe enough to warrant discontinuation,” he said. “Many obese persons today might wel be better off if they learned to live with their condition and stopped subjecting themselves over and over to painful and frustrating attempts to lose weight.”

More recent assessments of the efficacy of semi-starvation diets tend to be studies that set out to evaluate the efficacy of low-fat, calorie-restricted diets, but because they do so by comparing these diets with more balanced calorie-restricted diets, they provide evidence for the efficacy of the latter as wel . In 2002, a Cochrane Col aboration review of the evidence concluded that low-fat diets induced no more weight loss than calorie-restricted diets, and in both cases the weight loss achieved “was so smal as to be clinical y insignificant.” A similar analysis was published in 2001 by the U.S. Department of Agriculture. In this case, the authors identified twenty-eight relevant trials of low-fat diets, of which at least twenty were also calorie-restricted. The overweight subjects consumed, on average, less than seventeen hundred calories a day for an average weight loss of not quite nine pounds over six months. Only one of these studies tracked its participants for more than a year, and in that case the subjects reportedly reduced their caloric intake to thirteen hundred calories for eighteen months. In other words, these subjects reportedly consumed fewer calories per day than had Keys’s conscientious objectors, they maintained this semi-starvation regimen for three times as long—and they emerged from the trial having gained, on average, a pound. In the Women’s Health Initiative, discussed earlier (see Chapter 4) twenty thousand women were prescribed a low-fat diet and reportedly reduced their calorie consumption by an average of 360 calories a day. After almost eight years of this regimen, they weighed only two pounds less than when they started, and their average waist circumference, which is a measure of abdominal fat, had increased.

The evidence for the failure of semi-starvation as a treatment of obesity hasn’t stopped obesity researchers from recommending the approach. The Handbook of Obesity, published in 1998 and edited by three of the most prominent authorities in the field—George Bray, Claude Bouchard, and W.P.T.

James—says that “dietary therapy remains the cornerstone of treatment and the reduction of energy intake continues to be the basis of successful weight reduction programs.” It also notes, in contradiction, that the results of such calorie-restricted diets “are known to be poor and not long-lasting.” The chapter on obesity in the latest edition of Joslin’s Diabetes Mellitus, written by two clinical investigators from Harvard Medical School, also describes “reduction of caloric intake” as “the cornerstone of any therapy for obesity.” It then notes that reducing energy intake to a level substantial y below that of energy expenditure “is difficult to accomplish despite a wide variety of specific dietary approaches.” A deficit of seventy-five hundred calories, the authors explain, “is predicted to produce a weight loss of [2.2 pounds],” and so a reduction in food intake of a hundred calories a day “should bring about [an eleven-pound] weight loss over 1 year.” But this doesn’t seem to happen. “It is clear from common experience, however, that attempts at dieting that rely on such smal reduction in food intake are rarely successful. Thus, more severe reductions in energy intake are typical y prescribed,” the Harvard physicians write. These more severe regimens include total starvation, but “the extreme nature of the therapy,” the loss of muscle rather than fat tissue, and the many complications “have led to the virtual disappearance of this approach.” They also include very low-calorie diets of two to six hundred calories a day, which wil inevitably lead to weight loss, but the weight loss diminishes as the diet progresses, once again because metabolism and energy expenditure both decrease, and when the patients go off the diet, they regain the weight lost. Final y, there are the “many different diets” that provide eight hundred to a thousand calories and are in common use, al of which “should result in weight loss.” “None of these approaches,” the authors say, “has any proven merit.”

In response to these pessimistic assessments, it is commonly suggested that the obese would ameliorate their problem, or prevent it, if they merely exercised—perhaps sixty or ninety minutes a day, as now prescribed by the USDA Dietary Guidelines. A negative energy balance can be created, according to this logic, by increasing energy expenditure as wel as by eating less. Advice to engage in daily physical activity is now ever-present in public-health messages and popular writing on the problems of obesity and overweight. It’s reinforced by the existence of the ubiquitous electronic displays on stair-climbers, treadmil s, and other exercise apparatus that tel us how many calories we al egedly expended in our latest workout.

The belief in physical activity as a method of weight control is relatively new, however, and it has long been contradicted by the evidence. When Russel Wilder of the Mayo Clinic lectured on obesity in 1932, he noted that his patients tended to lose more weight with bed rest, “while unusual y strenuous physical exercise slows the rate of loss.” “The patient reasons quite correctly,” Wilder said, “that the more exercise he takes the more fat should be burned and that loss of weight should be in proportion, and he is discouraged to find that the scales reveal no progress.”

Until the 1960s, clinical investigators routinely pointed out that moderate exercise would lead only to insignificant increases in energy expenditure, and these could be easily matched by slight and comparatively effortless changes in diet. A 250-pound man wil expend three extra calories climbing a flight of stairs, as Louis Newburgh of the University of Michigan calculated in 1942, and this in turn is the equivalent of depriving himself of one-fourth of a teaspoon of sugar or a tenth of an ounce of butter. “He wil have to climb twenty flights of stairs to rid himself of the energy contained in one slice of bread!”

Newburgh observed.

Though more strenuous exercise would burn more calories, it would also lead to a significant increase in appetite. This is the implication of the phrase

“working up an appetite.” “Vigorous muscle exercise usual y results in immediate demand for a large meal,” noted the Northwestern University endocrinologist Hugo Rony in 1940. “Consistently high or low energy expenditures result in consistently high or low levels of appetite. Thus men doing heavy physical work spontaneously eat more than men engaged in sedentary occupations. Statistics show that the average daily caloric intake of lumberjacks is more than 5,000 calories while that of tailors is only about 2,500 calories. Persons who change their occupation from light to heavy work or vice versa soon develop corresponding changes in their appetite.”*77 If a tailor became a lumberjack and, by doing so, took to eating like one, there was little reason to think that the same wouldn’t happen, albeit on a lesser scale, to an obese tailor who chose to work out like a lumberjack for an hour a day.

In 1960, when the epidemiologist Alvan Feinstein examined the efficacy of various obesity treatments in a lengthy review in the Journal of Chronic Diseases, he dismissed exercise in a single paragraph. “There has been ample demonstration that exercise is an ineffective method of increasing energy output,” Feinstein noted, “since it takes far too much activity to burn up enough calories for a significant weight loss. In addition, physical exertion may evoke a desire for food so that the subsequent intake of calories may exceed what was lost during the exercise.”

By this time, though, exercise had a profoundly influential proponent: the Harvard nutritionist Jean Mayer, who would almost single-handedly overturn a century of clinical evidence and anecdotal experience. In the 1950s, when Mayer established himself as the leading authority on obesity in the United States, he did so based more on the romance of his background than his expertise as a clinical scientist: he was the son of the famous French physiologist André Mayer, and he had fought in the French resistance during World War I .

Mayer represented a new breed of obesity authority, of a kind that would now come to dominate the field. His predecessors—among them Louis Newburgh, Hugo Rony, Hilde Bruch, Frank Evans, Julius Bauer, and Russel Wilder—had al been physicians who worked closely with obese patients.

Col ectively, they had treated thousands of them. Their views on the cause of obesity differed, often radical y, but their firsthand experience was unquestionable. Mayer was not a clinician. His training was in physiological chemistry; he had obtained a doctorate at Yale on the interrelationship of vitamins A and C in rats. In the ensuing decades, he would publish hundreds of papers on different aspects of nutrition, including obesity, but he never treated obese patients, so his hypotheses were less fettered by any anecdotal or real-life experience.

As early as 1953, after just two years of research on genetical y obese mice, Mayer was extol ing the virtues of exercise for weight control. By the end of the decade, he was getting credit from the New York Times for having “debunked” the “popular theories,” argued by clinicians and their obese patients, that exercise had little influence on weight. Mayer knew that the obese often eat no more than the lean, and often even less. This seemed to exclude overeating, which meant the obese had to be less physical y active. Otherwise, how could they have achieved positive energy balance and become obese? Mayer himself first reported this phenomenon in a strain of laboratory mice that were prone to both obesity and diabetes. They ate little more than their lean littermates, he noted, but their activity was “almost nil” this sedentary behavior could explain their propensity to grow fat.