Our weight is determined by the number of calories we take in compared to the number of calories we expend. So, if you over-eat and don’t exercise, all those extra calories will be stored as fat, and the solution to losing the fat is to eat less and exercise more, right? What if this isn’t true?
For most people, over the long term, eating less doesn’t work, nutritionists David S. Ludwig and Mark I. Friedman write in an opinion piece for The New York Times. They suggest it is time to look at another idea, one that says overeating is not causing us to get fat, but that the process of getting fat is causing us to overeat.
This hypothesis suggests that when fat cells take in too many calories, those calories increase the amount of fat tissue instead of providing the energy our bodies need to function. When this happens our bodies still think we need food, so they continue to tell us we are hungry. Thus, we eat more and subsequently gain weight, Ludwig and Friedman write in The Journal of the American Medical Association.
Studies have shown our bodies have a “set point” for weight largely determined by our genes, Ludwig and Friedman note. If this is true, they then pose the question: Why has obesity almost tripled since 1960, and what can we do about it?
Ludwig and Friedman write that among the many biological factors that affect the storage of calories in fat cells, one has an indisputably dominant role: the hormone insulin. We know that excess insulin causes weight gain, and insulin deficiency causes weight loss. We also know that highly refined and rapidly digestible carbohydrates, like sugar or potatoes, produce the most insulin.
The authors suggest that the increasing amount of refined carbohydrates in Americans’ diets has “increased insulin levels, put fat cells into storage overdrive and elicited obesity-promoting biological responses in a large number of people.”
The authors suggest that one reason we consume so many refined carbohydrates is because they have been added to processed foods in place of fats, especially since low-fat diets are the most recommended diet. However, several studies cited in the article show that low-fat diets are the least effective way to lose weight.
The authors recognize that existing research cannot provide a definitive test of their hypothesis and the existing trials have exhibited major limitations, but it is time to “invest much more in this research.” The cost savings for treating diabetes alone—predicted to approach half a trillion dollars by 2020—would make it a good investment.
If this hypothesis turns out to be correct, the authors say obesity treatment would more appropriately focus on diet quality rather than calorie quantity.
“With reduced consumption of refined grains, concentrated sugar and potato products and a few other sensible lifestyle choices, our internal body weight control system should be able to do the rest,” they write. “Eventually, we could bring the body weight set point back to pre-epidemic levels. Addressing the underlying biological drive to overeat may make for a far more practical and effective solution to obesity than counting calories.”
David S. Ludwig directs the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital and is a professor of pediatrics at Harvard Medical School. Mark I. Friedman is vice president of research at the Nutrition Science Initiative.