Industry Figure Tom Chappell

(Back to Parts One, Two, or Three)

Suppose you have some lab rats. If offered rat chow, they’ll eat until they’re satisfied, and then stop. But what, exactly, triggers that satisfied feeling? What makes a rat happy? What makes a rat hungry?

Proponents of high-fiber diets claim that adding fiber to meals helps promote a feeling of fullness, without adding a lot of calories. Similar reasons are given for the often-heard advice to drink 8 cups of water every day — if you’re full on fiber and water, you won’t be hungry for bagels.

However…

The seminal experiments on this question were done by the University of Rochester physiologist Edward Adolph back in the 1940s. Adolph diluted the diets of his rats with water, fiber, and even clay, and noted that the rats would continue to eat these adulterated diets until they consumed the same amount of calories they had been eating when he had fed them unadulterated rat chow. The more Adolph diluted the chow with water, the more the rats consumed — until the meals were more than 97 percent water. At these very low dilutions, the rats apparently expended so much energy drinking that they couldn’t consume enough calories to balance the expenditure. When Adolph put 90 percent of their daily calories directly into their stomachs, “other food was practically refused for the remainder of the twenty-four hour period.” Putting water into their stomachs had no such effect.

…from Good Calories, Bad Calories (Knopf, 2007), by Gary Taubes, p. 309

Hunger was being driven, not by the stomach being full, but by the immediate needs of the body’s cells being satisfied, regardless of the size of the fat stores that might be available elsewhere for long-term use, and our old friend insulin turns out to be a key player here, as well.

Even miniscule amounts of insulin cause fat cells to stop releasing free fatty acids into the bloodstream, and to start taking up glucose and free fatty acids and storing them as triglycerides. Fuel is swept out of the bloodstream and back in the fat cells, reducing the fuel available to the rest of the body’s cells, which the brain registers as hunger.

Anorexics, for example, if given a shot of insulin, will eat, and put on weight. And this is no placebo effect; it can also be seen in our friends, the rats. Infuse insulin into a rat, even a sleeping rat, and it will immediately awaken and begin eating, and will continue to eat as long as the insulin infusion continues.

What’s been clear for almost forty years is that the levels of circulating insulin in animals and humans will be proportional to body fat. “The leaner an individual, the lower his basal insulin, and vice versa,” as Stephen Woods, now director of the Obesity Research Center at the University of Cincinnati, and his colleague Dan Porte observed in 1976. “This relationship has also been shown to occur in every commonly used model of altered body weight, including…genetically obese rodents and overfed humans. In fact, the relationship is sufficiently robust that it exists in the presence of widespread metabolic disorder, such as diabetes mellitus, i.e. obese diabetics have elevated basal insulin levels in proportion to their body weight.” Woods and Porte also noted that when they fattened rats to “different proportions of their normal weights,” this same relationship between insulin and weight held true. “There are no known major exceptions to this correlation,” they concluded. Even the seasonal weight fluctuations in hibernators agree with the correlation; the evidence suggests that annual fluctuations in insulin secretion drive the yearly cycle of weight and eating behavior, although this has never been established with certainty.

…from Good Calories, Bad Calories (Knopf, 2007), by Gary Taubes, p. 439

Note, too, that someone who is insulin-resistant doesn’t have to wait for his blood sugar levels to fall to become hungry from higher insulin levels. His non-fat cells cannot easily use glucose, and with insulin levels high, his fat cells aren’t releasing the free fatty acids that his non-fat cells are capable of using well. Despite high blood glucose levels, the insulin-resistant person’s non-fat cells are starved, and he’s hungry. If he’s trying to diet by one of the low-calorie, high-carbohydrate diets such as Pritikin, he’s ravenous.

All right, we’ve got to get insulin levels down, but how? Tune in next time, when once again the rats will show the way.

Continued in Part Five…