overeating—the vast majority—are making the kind of mistake that would (or at least should) earn a failing grade in a high-school science class. They’re taking a law of nature that says absolutely nothing about why we get fat and a phenomenon that has to happen if we do get fat—overeating—and assuming these say all that needs to be said. This was a common error in the first half of the twentieth century. It’s become ubiquitous since. We need to look elsewhere for answers.
A good place to start might be a National Institutes of Health report published back in 1998. Back then, the NIH experts were a little more forthcoming, and so a little more scientific, about the factors that might cause obesity: “Obesity is a complex, multifactorial chronic disease that develops from an interaction of genotype and the environment,” they explained. “Our understanding of how and why obesity develops is incomplete, but involves the integration of social, behavioral, cultural, physiological, metabolic and genetic factors.”
So maybe the answers to be found are in this integration of factors—starting with the physiological, metabolic, and genetic ones and letting them lead us to the environmental triggers. Because the one thing we should know for sure is that the laws of thermodynamics, true as they always are, tell us nothing about why we get fat or why we take in more calories than we expend while it’s happening.
* It is possible to get fatter without getting heavier if we lose muscle and gain fat. Then we don’t have to take in more energy than we expend because we might be moving energy from the muscle to the fat. That’s why I say fatter and heavier, rather than just fatter.
* Jean Mayer, who got a few things right about obesity and weight regulation but the important things wrong, phrased the issue this way back in 1954: “Obesity, too many people believe, is
explained
by overeating; actually it should be recognized that this is simply restating the problem in a different way, and reaffirming (somewhat unnecessarily …) one’s faith in the First Law of Thermodynamics. To ‘explain’ obesity by overeating is as illuminating a statement as an ‘explanation’ of alcoholism by chronic overdrinking.”
7
Thermodynamics for Dummies, Part 2
Before leaving thermodynamics behind, let’s clear up one more misguided extrapolation of these laws to the world of diet and weight. The very notion that expending more energy than we take in—eating less and exercising more—can cure us of our weight problem, make us permanently leaner and lighter, is based on yet another assumption about the laws of thermodynamics that happens to be incorrect.
The assumption is that the energy we consume and the energy we expend have little influence on each other, that we can consciously change one and it will have no consequence on the other, and vice versa. The thinking is that we can choose to eat less, or semi-starve ourselves (reduce calories-in), and this will have no effect on how much energy we subsequently expend (calories-out) or, for that matter, how hungry we become. We’ll feel just as full of pep if we eat twenty-five hundred calories a day as if we consume half that amount. And by the same token, if we increase our expenditure of energy, it will have no influence on how hungry we become (we won’t work up an appetite) or on how much energy we expend when we’re not exercising.
Intuitively we know this isn’t true, and the research in both animals and humans, going back a century, confirms it. People who semi-starve themselves, or who are semi-starved during wars, famines, or scientific experiments, are not only hungry all thetime (not to mention cranky and depressed) but lethargic, and they expend less energy. Their body temperatures drop; they tend to be cold all the time. And increasing physical activity
does
increase hunger; exercise does work up an appetite; lumberjacks do eat more than tailors. Physical
A good place to start might be a National Institutes of Health report published back in 1998. Back then, the NIH experts were a little more forthcoming, and so a little more scientific, about the factors that might cause obesity: “Obesity is a complex, multifactorial chronic disease that develops from an interaction of genotype and the environment,” they explained. “Our understanding of how and why obesity develops is incomplete, but involves the integration of social, behavioral, cultural, physiological, metabolic and genetic factors.”
So maybe the answers to be found are in this integration of factors—starting with the physiological, metabolic, and genetic ones and letting them lead us to the environmental triggers. Because the one thing we should know for sure is that the laws of thermodynamics, true as they always are, tell us nothing about why we get fat or why we take in more calories than we expend while it’s happening.
* It is possible to get fatter without getting heavier if we lose muscle and gain fat. Then we don’t have to take in more energy than we expend because we might be moving energy from the muscle to the fat. That’s why I say fatter and heavier, rather than just fatter.
* Jean Mayer, who got a few things right about obesity and weight regulation but the important things wrong, phrased the issue this way back in 1954: “Obesity, too many people believe, is
explained
by overeating; actually it should be recognized that this is simply restating the problem in a different way, and reaffirming (somewhat unnecessarily …) one’s faith in the First Law of Thermodynamics. To ‘explain’ obesity by overeating is as illuminating a statement as an ‘explanation’ of alcoholism by chronic overdrinking.”
7
Thermodynamics for Dummies, Part 2
Before leaving thermodynamics behind, let’s clear up one more misguided extrapolation of these laws to the world of diet and weight. The very notion that expending more energy than we take in—eating less and exercising more—can cure us of our weight problem, make us permanently leaner and lighter, is based on yet another assumption about the laws of thermodynamics that happens to be incorrect.
The assumption is that the energy we consume and the energy we expend have little influence on each other, that we can consciously change one and it will have no consequence on the other, and vice versa. The thinking is that we can choose to eat less, or semi-starve ourselves (reduce calories-in), and this will have no effect on how much energy we subsequently expend (calories-out) or, for that matter, how hungry we become. We’ll feel just as full of pep if we eat twenty-five hundred calories a day as if we consume half that amount. And by the same token, if we increase our expenditure of energy, it will have no influence on how hungry we become (we won’t work up an appetite) or on how much energy we expend when we’re not exercising.
Intuitively we know this isn’t true, and the research in both animals and humans, going back a century, confirms it. People who semi-starve themselves, or who are semi-starved during wars, famines, or scientific experiments, are not only hungry all thetime (not to mention cranky and depressed) but lethargic, and they expend less energy. Their body temperatures drop; they tend to be cold all the time. And increasing physical activity
does
increase hunger; exercise does work up an appetite; lumberjacks do eat more than tailors. Physical
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