The Doctor Weighs In

Yesterday’s New York Times ( May 8, 2007 ) carried a front page article by one of the paper’s premier science reporters, Gina Kolata. The article, titled “genes take charge, and diets fall by the wayside”, is an excerpt of her newly published book “Rethinking thin: the new science of weight loss- and the myths and realities of weight loss”. In the article she reviews the succession of studies started in the late 1950’s by Dr Jules Hirsch at Rockefeller University , which culminated in recent studies demonstrating conclusively that the tendency to weight gain and obesity is genetically determined. Ms. Kolata describes the heartbreak of dieting, a constant struggle of losing weight, trying to maintain, gaining, dieting again, and so on and so on. Psychological testing showed the toll this struggle can take; people are perpetually unhappy, many are chronically depressed, some are suicidal.

One of the major conclusions Kolata cites is that each body has a metabolic “comfort zone”, and dieting to go below this zone is painful, metabolically unsound, and essentially futile.

I admit I haven’t read the book yet, but if the excerpt reflects the message of the book, I strongly disagree.

Why?

For several reasons:

· Yes, a metabolic range specific to each body makes a lot of intuitive sense. But to accept it we need to see the genetic/molecular/physiological mechanisms. The evidence is still not in. Having been around the block a few times, I never cease to marvel at nature outsmarting us, and upending our ‘no brainers’ and ‘slam dunks’.

· The fact that genes control our metabolism does not mean that they are the sole players. Genes interact with the environment, and the outcome of this interaction is all important. The old debate of nature vs. nurture set up a false choice; nature and nurture operate together in biology. The best example is diabetes type 2. An individual may have the genes that predispose to this disease. But it will be expressed clinically only if that individual overeats and exceeds a certain BMI.

· The most obvious evidence that genes are not the final word in weight regulation is the recent obesity epidemic. If  "obesity genes",which undoubtedly have been with us for eons, were such an all-controlling factor, why is it that only in the last few years did this epidemic break out? The answer is well-known: we take in a lot more calories, and we exercise a lot less. Yes, the genes were there all along, but they were not expressed.

I believe that research into the genetic basis of obesity and diabetes is absolutely essential. But it should not become an excuse for the fatalistic attitude of “it’s beyond my control”. Counteracting and ovecoming the genetic dictate may be unpleasant, tough, exasperating—but it beats the alternative.

Dov Michaeli MD, Ph.D