The worldwide obesity crisis has yielded too many overhyped solutions, and not enough solid evidence. Everyone's got a favorite approach: drink more water, eat a bigger breakfast, fast every other day, exercise more, avoid fatty foods, load up on high-volume salads, go vegan, exclude gluten, live like a caveman, and on and on and on.

Despite all the "answers," people keep gaining weight and losing health. This often provokes the classicists to proclaim their KISS (Keep It Simple, Stupid) philosophy: The calorie is king. Eat fewer calories, burn more, and you'll lose weight.

Last week, two bastions of medical science--The New England Journal of Medicine (NEJM) and the Journal of the American Medical Association (JAMA)--published essays casting doubt on that classic view. Coming from traditional medical journals, this was news. The JAMA article was expanded into a section-opening headliner in the Sunday New York Times titled "Always Hungry? Here's Why." [See end of this post for links.]

In the NEJM article, Harvard professor Chin Jou, Ph.D., from the Department of the History of Science, summarizes research on the genetics of obesity. Several landmark studies of adopted children, or twins raised in different homes, have shown that the home environment had less effect than the child's family of origin.

Another famous study followed 12 adult twins who were overfed by 84,000 calories during a 100-day period. Classic thermodynamics--calories in/calories out--would predict that all 24 individuals should gain 24 pounds (84,000/3,500 calories per pound). Instead they gained from 9.5 lbs to 29 pounds. However, there was much less variation in weight gain within twin pairs, and even less in fat gain.

Chu concludes: "The views of many Americans notwithstanding, weight is clearly far from being entirely within an individual's control. Genetic predispositions may help explain why so many Americans are obese today."

An accompanying research article in the NEJM identified a gene, DYRK1B, present in all members of several families who developed obesity/heart disease/diabetes/high blood pressure, but lacking in other families.

The JAMA article was co-authored by Mark Friedman, Ph.D., and David Ludwig, M.D., Ph.D., of the New Balance Foundation Obesity Prevention Center at Boston Children's Hospital. (Yes, that New Balance, the running shoe company.)

They provocatively propose that overeating doesn't cause obesity, but rather that obesity causes overeating. In their model, this happens when too many sugars and processed carbohydrates spike the body's insulin levels, leading to fat deposits. "Subsequently, hunger increases and energy expenditure decreases," Ludwig and Friedman write, because potentially useful fuel has been shunted into fat cells.

This hunger causes the individual to reach for the next readily-available processed foods, and the cycle continues, Friedman and and Ludwig say. To break the cycle, they propose low-glycemic foods including protein, healthy fats, whole grains, and vegetables. Ludwig and Friedman admit that diet-quality studies (i.e., low-carb vs. high-carb diets) have yet to prove their hypothesis, but believe that future research will.

"Overeating may be secondary to diet-induced metabolic dysfunction in the development of some forms of obesity," they write. "If so, treatment focused on dietary quality, rather than advice to eat less, could produce better long-term weight loss."

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