Rethinking Thin: The New Science of Weight Loss
As anyone who’s studied the research will know, the bottom line for dieters is discouraging. Well-documented, rigorous, objective studies tell us that “normal” people have a genetically determined weight range beyond which efforts to either gain or lose weight will be counterbalanced by the body’s metabolism, which speeds up or slows down to compensate for more or fewer calories. There are other side effects, too, like developing an obsession with food and binge eating. The range can run up to about 30 pounds in either direction; research indicates that at best, dieters can sustain a 5 to 10 percent weight loss, after which their bodies will tend to return to a stable weight over the course of time.
Interestingly — here’s where some of the newer research comes in — studies suggest that leptin can change the brain’s “wiring” in young and adult animals, permanently changing their appetite and weight. This might explain why some people grow obeseMore work is being done now on signals, such as the stomach’s release of ghrelin, which activates the production of appetite-stimulating peptides, and PYY, a peptide that reflects the calorie content of a meal and blocks the nerves stimulated by ghrelin to make you feel sated. A preliminary study of PYY injections indicates that it does block appetite in humans, and efforts to develop a useful drug are still underway, although going slowly. Another peptide called oxyntomodulin is also being studied as an appetite suppressant, though it has only a short-term effect (hours, rather than a day). People who’ve had gastric bypass surgery apparently produce more PYY and oxyntomodulin than they did before, which is why their appetite decreases (their digestion functions return to normal within three or four days, just moving down the bowel farther than normal).
In addition, studies of people who’ve had bariatric surgery shows that while post-surgery patients have less diabetes ten years after the study began than the control group, blood pressure and cholesterol returned to pre-surgery levels within two years after the operation. Similar results were found for women who’d had fat removed through liposuction. So, weight loss might be useful for diabetics, but not necessarily to combat high blood pressure or cholesterol levels.
Moreover, again as hard-core readers of obesity studies will already be aware, there’s compelling evidence that the obese have lower mortality rates than the “normal” or underweight. Kolata discusses the furor over this finding at some length but leaves you convinced that studies refuting the finding are statistically flawed. However, by the time you’re 70, having a bit of extra fat may be beneficial, stimulating the body to make more muscle and bone. Other research shows a trend around the world that as populations grow healthier, newer generations become taller and fatter — the highest death rates fall at the lowest and highest body mass indices, with the best weights for health including weights currently considered “overweight.”
This book, then, questions two deeply held American beliefs: if you’re fat, you can lose weight and keep it off if you try hard enough, and if you lose weight, you’ll be as healthy as someone who was never fat. The fact is, if you’re fat, you can lose weight to a point, but after that, your body will compensate for further calorie reduction. Radical procedures like gastric bypass surgery or, perhaps in the future, chemical treatments, may work, but exercise and calorie reduction have clear limits. In addition, it may be that moderate obesity is less of a health risk than expected. Certainly, nobody is arguing that the grossly obese have serious health risks, but just being fat? Maybe not. In fact, America’s “obesity epidemic” may be “an unintended consequence of the nation’s generally better health, or maybe even a contributor to it” (p. 222).
Kolata is a science writer for the New York Times and puts everything together in a chronological study in which you can see how one finding leads to another, and how “breakthroughs” are sent back to the drawing board as scientists discover that weight gain and loss isn’t as straightforward as they’d thought. Like most other books of its type, it will no doubt sink into obscurity, “outweighed” by the multimillion-dollar diet industry that has absolutely no interest in letting dieters know that their weight goals are probably unrealistic and unsustainable over the long term. But for anyone who’s struggled with diets, it’ll provide a useful reality check to the grinding and false belief that fatness equals lack of self-discipline.
drupagliassotti @ June 28, 2007