The QOTD, on the idea that “a calorie is a calorie:”
“The first experiments were the inspiration of a scientist, Ethan Sims of the University of Vermont, who asked what would happen if thin people who had never had a weight problem deliberately got fat… Sims says he got the idea from research he had done during a sabbatical year, when he was trying to make mice fat. That turned out to be difficult – even when they were supplied with abundant tasty food, the mice ate only enough to maintain their weight. Sims could force-feed the animals, but then they would increase their metabolic rate and burn more calories, which led them to gain less than was predicted. Even if the animals put on some weight, they would lose it and go right back to their original weights when the study ended. Sims began to wonder whether people, too, would have a hard time gaining weight. No one had ever really asked – who, after all, would want to get fat?
But Sims was a university faculty member, and when he returned to the University of Vermont he managed to find subjects for his weight-gain study among its students. He deliberately recruited students who had never been fat and had no family history of obesity and who were willing to make a serious effort to try to become fat. It sounded as if it would be easy – all you would have to do is indulge yourself with all of your favorite calorie-laden treats. Most people, when asked, say they could weigh much more than they do but that they exert their willpower to keep the weight down.
But Sims and his student volunteers found otherwise. To their own surprise, these subjects found it all but impossible to gain much weight; no matter how much they tried to eat, they just could not become obese…
Maybe, Sims decided, the problem was that the volunteers were free to move about and were burning too many calories with physical activity. He thought of the perfect subjects, people who really would have no chance to cheat and burn off calories: prisoners. So he repeated his experiment with men who were incarcerated in a nearby state prison and who volunteered to become fat.
This time, the experiment worked, in a fashion – the men got fat. But producing obesity turned out to be much harder than Sims had anticipated. The men increased their weight by 20 to 25 percent, but it took four to six months for them to do this, eating as much as they could every day. Some ended up eating 10,000 calories a day, an amount so incredible that it would be hard to believe, were it not for the fact that the research study had attendants present at each meal who dutifully recorded everything the men ate.
But when Sims calculated the amount of weight the men should be gaining, he discovered that they were gaining much less than would have been predicted and that different men gained at different rates. Once the men were fat, Sims asked how many calories they needed to maintain their weight, and how that compared with the calories they needed when they were at their normal weights, before the study began. The answer was astonishing: When the thin men got fat, their metabolism increased by 50 percent. they needed more then 2,700 calories per square meter of their body surface to stay at their obese weight, but just 1,800 calories per square meter to maintain their normal weight…
Then Sims did another study. He recruited very heavy men and dieted them down to the same level of fatness as the newly obese prisoners. These men, while just as fat as the prisoners, needed half as many calories to maintain their weight…
As for the fat cells of the newly obese prisoners, it turned out that they had simply grown larger, much larger, but their number remained constant. The men were fat, but they got that way by stuffing the cells they already had with globules of fat, not by growing more fat cells. So, because they always had fewer fat cells than people who were naturally fat, they were fundamentally different from naturally fat people.
When the study ended, the prisoners had no trouble losing weight; within months, they were back to normal and effortlessly stayed there.
The implications were clear. There is a reason that fat people can’t stay thin after they diet and that thin people can’t stay fat when they force themselves to gain weight. The body’s metabolism speeds up or slows down to keep weight within a narrow range. Gain weight and the metabolism can as much as double; lose weight and the metabolism can slow down to half its original speed.”
- Gina Kolata, Rethinking Thin, pg. 116-18.