Always Hungry? It's Probably Not Your Insulin.

David Ludwig, MD, recently published a new book titled Always Hungry? Conquer cravings, retrain your fat cells, and lose weight permanently.  The book is getting widespread media coverage.  Ludwig is a professor of pediatrics at the Harvard Medical School and a professor of nutrition at the Harvard School of Public Health.  He's a pediatric endocrinologist, but his primary focus is research, particularly the impact of nutrition on hunger, calorie expenditure, and body weight.  Although I sometimes disagree with how he interprets evidence, he has made significant and useful contributions to the scientific literature in these areas, and I also support his efforts to find policy solutions to curb the intake of sweetened beverages and other junk foods.  In the grand scheme of things, he's an ally in the fight to improve the American diet.

Ludwig has written several high-profile op-ed pieces in recent years, both in the popular press and in scientific journals (1, 2).  He argues that our understanding of eating behavior and obesity may be all wrong, and that our focus on calories may be leading us away from the true cause of obesity: hormonal imbalance.  And the primary culprit is insulin.  You might recognize this idea, because it's similar to the one that science journalist Gary Taubes developed in his book Good Calories, Bad Calories.

According to this view, overeating is irrelevant.  We gain fat because our insulin levels are too high, leading our fat tissue to take up too much fat, and other tissues to take up too much glucose, causing our blood energy levels to drop and resulting in fat gain, hunger, and fatigue.  The ultimate cause of the problem is the rapidly-digesting carbohydrate and sugar we eat.  This idea is encapsulated by Ludwig's quote, "Overeating doesn't make you fat.  The process of getting fat makes you overeat" (3).

Here are eleven facts that may make you question this line of reasoning:
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