When Scientific Paradigms Collide

What if overeating doesn’t make you fat?

This post expands upon, and was modified from, an opinion article in The Washington Post

Most science operates under “normal” conditions, according to the famous philosopher Thomas Kuhn. Normal science aims to develop and refine a conventional way of thinking about nature — a paradigm — not overturn it. Because conventional thinking usually rests on years (sometimes centuries) of research, scientists are naturally skeptical of radical new paradigms.

Occasionally, problems with normal science arise, such as persistent failure to solve important puzzles and anomalies that can’t be easily explained away. When this happens, science may enter what Kuhn called a “crisis,” and competing paradigms emerge.

In a new paper in European Journal of Clinical Nutrition, my coauthors and I argue that the field of obesity is entering a crisis. To stem the rising tide of obesity-related disease, we must embrace, not resist, paradigm clash.

THE USUAL WAY of thinking about obesity is based on the notion of energy balance. Surrounded by delicious, energy-dense foods, we easily consume more calories than we need. This surplus is deposited into body fat, and we gain weight. Overeating causes obesity. According to this view, all calories are alike to the body, so the only way to lose weight is to eat fewer of them or burn more off with exercise.

For the past century, obesity prevention and treatment has been based on this notion of energy balance: from the original approach of calorie-counting in the early 1900s, to the low-fat diet craze of the late 1900s (targeting the most energy dense nutrient), to the recent focus on a range of modern processed foods high in fat and sugar.

In one way, this incessant focus on calories finally appears to be working. A new analysis by Dariush Mozaffarian of Tufts University concluded that, after a 3-decade increase, calorie consumption in the U.S. has decreased slightly since 2000. But obesity rates have increased by more than a third since then, to almost half of the population today. This paradox can’t be explained by our sedentary lifestyles — Americans have become more physically active over the last 2 decades.