Good Calories, Bad Calories (56 page)

At least some of these excess calories are lost in the various chemical reactions required to digest and store the nutrients. Rubner referred to this as the heat generated by the “thermochemical tangle of breakdowns” that occur during the process of digestion. Physicians measure basal or resting metabolism after a twelve-to-eighteen-hour fast because by then this diet-induced thermogenesis has played itself out. The protein in the diet, as Rubner discovered, dominates this effect. The more protein digested over the amount necessary to maintain tissues and organs, the greater the heat generation.

It’s what Rubner cal ed the specific dynamic effect of protein that is usual y invoked as the rationale to eat high-protein diets for weight loss; excessive calories lost as heat in the process of digesting and utilizing protein can’t then be stored as fat or used for fuel.

As the external environment changes, though, our bodies change the manner in which they utilize this heat. Maintaining our bodies at a constant temperature (roughly 98.6°F) requires more energy when it’s cold than when it’s warm. More of the heat from this thermochemical tangle of breakdowns, as Rubner reported, wil go to that purpose when it’s cold, as it wil when our energy reserves are low—when we’re undernourished—and we need to conserve the biological y useful energy for other purposes. In short, we wil put this heat to use when we need to conserve energy, and we wil waste it when it might be to our benefit to avoid the accumulation of excess calories as fat.

The primary source of controversy today remains the question that Rubner and Voit disputed a hundred years ago: whether the excess calories consumed have to be dissipated entirely as heat, or whether they can also be used biological y. Rubner argued that the energy requirements of our cel s are basical y constant. Under some set requirement, determined by temperature among other factors, our cel s wil adjust by conserving energy. Anything greater, and the energy is wasted as heat. Voit believed that the metabolic rate of our cel s responds to the fuel available. The more fuel, the more energy generated. According to Voit, overeating leads to an increase in the available energy for cel s, tissues, and muscles, and so perhaps to what the clinical investigators studying obesity in the first half of the century cal ed the “impulse to physical activity” or the “impulse to move.” That feeling of restlessness, they believed, is the manifestation of cel s and tissues, literal y, having energy to burn.

Both interpretations suggest the same fundamental conclusion about how our bodies work. We have thrifty metabolisms when we are undernourished and so need to use efficiently every calorie we consume, and we have spendthrift metabolisms when we’re overnourished, so as to avoid excessive weight gain and obesity. Our cel s may have a certain maximal or ideal capacity for metabolizing nutrients, but the amount that they actual y metabolize is ultimately determined by the quantity and perhaps the quality of the nutrients delivered in the circulation. This determination is made on a cel ular and hormonal level, not a cognitive or conscious one.

This idea that energy expenditure increases to match consumption, and that the ability to do this differs among individuals, also serves to reverse the cause-and-effect relationship between weight and physical activity or inactivity. Lean people are more active than obese people, or they have, pound for pound, a higher expenditure of energy,*89 because a greater proportion of the energy they consume is made available to their cel s and tissues for energy.

By this conception, lean people become marathon runners because they have more energy to burn for physical activity; their cel s have access to a greater proportion of the calories they consume to use for energy. Less goes to making fat. That’s why they’re lean. Running marathons, however, wil not make fat people lean, even if they can get themselves to do it, because their bodies wil adjust to the extra expenditure of energy, just as they would adjust to calorie-restricted diets.

Our propensity to alter our behavior in response to physiological needs is what the Johns Hopkins physiologist Curt Richter cal ed, in a heralded 1942

lecture, “total self-regulatory functions.” Behavioral adaptation is one of the fundamental mechanisms by which animals and humans maintain homeostasis. Our responses to hunger and thirst are manifestations of this, replenishing calories or essential nutrients or fluids. Physical activity, as Richter suggested, is another example of this behavioral regulation, in response to an excess or dearth of calories. “We may regard the great physical activity of many normal individuals, the play activity of children, and perhaps even the excessive activity of many manic patients, as efforts to maintain a constant internal balance by expending excessive amounts of energy,” he explained. “On the other hand, the low level of activity seen in some apparently normal people, the almost total inactivity seen in depressed patients, again may be regarded as an effort to conserve enough energy to maintain a constant internal balance.”

In 1936, when Eugene Du Bois published the third edition of his metabolism textbook, Basal Metabolism in Health and Disease, he described the system that accomplished the regulation of a stable body weight as it was then understood. How much we want to eat on any given day, Du Bois explained, is determined by how much we’ve depleted whatever our body considers the necessary reserves of protein, fat, and carbohydrates. If we then consume more calories than we need, the excess wil either be burned off as heat or induce physical activity: “When wel nourished, the individual tends to become more energetic and it is quite possible that he wil soon burn up his stored fat by extra work or exercise which would not have been undertaken had it not been for the overfeeding.” If we consume less food than we might require to replenish our reserves, then the amount of heat generated in response to a meal is minimized, and the stores of carbohydrates (glycogen), fat, and protein are used to make up the difference. Should the caloric deficit continue, the result is “a gradual lowering of metabolism and a tendency toward restriction of activities, due to a lack of energy and initiative.”

However this homeostatic system works to balance energy intake and output and thus maintain a steady supply of fuel to the cel s and a stable body weight, it is extraordinarily complex and involves the entire body. Rony discussed this: “The appetite mechanism, which is but a part, although the most important one, of body weight regulation is in itself a highly complex mechanism involving [the central nervous system], endocrine glands, the gastric neuro-muscular apparatus, and the organs of the glycogen, protein, and fat reserves.” This notion was supported by a host of experimental and clinical studies, as we’l discuss in Chapter 21, which demonstrated that disturbances in body-weight regulation—like obesity—could be caused by “pathological changes in certain parts of the nervous system, endocrine system and depot organs.”

It is also vital to understand that it’s our cel s and tissues that require and expend the energy we consume, so this adjustment of intake to expenditure is occurring first and foremost on a cel ular level. “Whatever may be the mechanisms control ing food intake,” as the University of California, Berkeley, nutritionist Samuel Lepkovsky wrote in 1948, “the chief site of their action must be the cel .” A fundamental requirement of any living organism is to provide a steady and reliable supply of fuel to its cel s, regardless of the circumstances. We apparently evolved an intricate and extraordinarily robust regulatory system of hormones, enzymes, and the nervous system to accomplish this task. If the necessary fuel fails to reach the cel s, the body compensates. The crucial factor is not how much is eaten—how many calories are consumed—or how much is expended, but how those nutrients or the energy they contain is ultimately distributed, how those calories are utilized and made available when needed. It’s not the energy balance that is driving this system, but the distribution of that energy, the demand for energy at the cel ular level.

FATTENING DIETS

Oversupply of food does not necessarily produce excessive nutrition. The appropriation depends in part on the character of the food and the ease or difficulty with which it is converted into a condition suitable for absorption, in part on such extrinsic and intrinsic influences as heredity, age, sexual and psychical habits, exercise and sleep; but to a great extent also on personal peculiarities of the metabolic processes….

JAMES FRENCH, The Practice of Medicine, 1907

IN 1857, JOHN HANNNING SPEKE AND Richard Burton set off through West Africa to search for the source of the Nile River. After Burton fel il, Speke discovered the river’s origin on his own. When he returned to the region five years later, according to his memoirs, he heard about the custom of local Abyssinian nobility to fatten up their wives to “such an extent that they could not stand upright.” He went to see for himself. “There was no mistake about it,”

he recal ed. “On entering the hut I found the old man and his chief wife sitting side by side on a bench…. I was struck with the extraordinary dimensions, yet pleasing beauty, of the immoderately fat fair one his wife. She could not rise; and so large were her arms that, between the joints, the flesh hung down like large, loose stuffed puddings.” Two weeks later, when Speke visited “another one of those wonders of obesity,” he took the opportunity to measure her. Her chest was fifty-two inches around. Her arms were nearly two feet in circumference and her thighs over two and a half feet.

With the notable exception of the current prevalence of obesity in Western societies, there is little reason to believe that fattening up the constitutional y lean is any easier than inducing leanness in the obese. For successful fattening, the excess calories consumed have to be stored as fat, rather than expended in metabolism or physical activity or stored as muscle. This isn’t a given, considering these alternative uses for the calories. Continuing to consume excess calories is necessary, too—the person being fattened has to continue eating long after becoming sated—and these calories also have to be stored as fat.

In the early 1970s, the British physician John Garrow attempted to add twelve hundred calories a day to his daily diet, hoping to sustain it for a hundred days. After failing with several methods, he found that he could accomplish his goal by keeping chocolate biscuits on hand and, “whenever the prospect didn’t seem too revolting, eating however many of these biscuits that I could.” He managed to gain fifteen pounds in sixty days and then gave up the experiment and lost the weight in fifty days. “I learned that for me it is difficult to move my weight at al rapidly in any direction,” he said, “and I saw absolutely no reason to suppose that obese people would find it easier than I did.”

Various foods have been used to induce extensive fattening. The tribes that Speke visited relied on milk to fatten their women. In the mid-1970s, the French ethnologist Igor de Garine documented two male fattening sessions of the Massa tribe of northern Cameroon. In an individual ritual, the man ingests both milk and a porridge made from sorghum, a cornlike grain that provides, like sugarcane, a sweet syrup from the stalk. In 1976, Garine reported, one Massa tribesman gained seventy-five pounds on this ceremonial binge, apparently averaging ten thousand calories a day throughout. In a group fattening ritual, the men consume thirty-five hundred calories a day, rather than their usual twenty-five hundred, the excess consiting of milk and porridge. The weight gain tends to be fifteen to twenty pounds. The Massa are cattle herders, and their staple diet is primarily milk. This fattening, therefore, is accomplished by the addition of carbohydrates almost exclusively—one thousand to seventy-five hundred calories a day of sorghum.

The sumo wrestlers of Japan, whose weight commonly exceeds three hundred pounds, typical y reach that level by their early twenties. In 1976, a University of Tokyo col aboration, led by Tsuneo Nishizawa, published an article in The American Journal of Clinical Nutrition that stil constitutes the most comprehensive analysis in the English medical literature of the sumo diet, body composition, and health. The world of professional sumo wrestling, according to Nishizawa, is divided into an “upper group,” constituting the best wrestlers in the country, and a “lower group.” The members of the upper group consumed on average some fifty-five hundred calories’ worth of chanko nabe (a pork stew) a day, out of which 780 grams were carbohydrates, 100 grams fat and 365 grams protein. This constituted more than twice the calories and carbohydrates of the typical Japanese diet of the era,*90 slightly less than twice the fat, and four and a half times the amount of protein. The sumo diet was very high in carbohydrate by our standards—57 percent of the calories—and very low in fat—16 percent—considerably beneath what most public-health authorities in America consider a feasible low-fat target. The lower group of sumo weighed as much as their more accomplished col eagues, but were significantly fatter and less muscular. They consumed, on average, only 5,120 calories of chanko nabe a day, consisting of 1,000 grams of carbohydrates, 165 grams of protein, and only 50 grams of fat; these lesser sumo attained and maintained their corpulence on a diet of nearly 80 percent carbohydrate calories and 9 percent fat.

It seems that if we wanted to design a diet capable of inducing pathological obesity in young men in their prime, we might start with just such a very low-fat, high-carbohydrate diet. The diet would provide an enormous amount of calories, which might be the salient factor, but we would have to wonder what it is about this dietary composition that al ows for such extraordinary overconsumption, not just for a few days, but for years or perhaps decades.

For the past quarter century, public-health authorities and obesity researchers have insisted that it is dietary fat, not carbohydrates, that fattens most effectively and causes obesity. This is why low-fat, low-calorie diets are recommended for weight loss as wel as prevention of heart disease. This notion is based on four pieces of evidence, al of which are easily chal enged.