Fitness scientist and bodybuilder Dr. Layne Norton recently took aim at a post made by Dr. Jason Fung, in which Fung claimed, “You’re not fat because you overeat. You overeat because you’re fat.” Norton did not hold back.
“Eating more does not make us fat. Getting fat makes us eat more. Overeating is not a personal choice. It is a hormonally driven behavior, a natural consequence of increased hunger hormones,” Norton quoted from Fung’s post, before breaking down exactly where the argument falls apart.
Norton acknowledged a partial truth in the claim: “We know people who are obese tend to have differential responses to food compared to people who are lean. People who are prone to obesity get a greater reward from food. They tend to be hungrier and have greater appetite and drive to eat.”
However, he was clear that conceding that point does not validate Fung’s conclusion.
“The idea that obesity is not caused by overeating, but rather if you’re fat, you tend to overeat in response, it’s kind of a chicken or the egg argument. And he is absolutely wrong,” Norton said.
Norton explained that Fung is a proponent of the carbohydrate insulin model of obesity, which holds that elevated insulin traps fat inside fat cells, making it inaccessible to the rest of the body, causing a person to overeat because their body senses it is starving. Norton argued this model has been debunked on multiple levels.
His first point centered on GLP-1 treatments, currently the most effective obesity treatment available.
“What do those GLP-1s do? Not only do they drastically decrease your hunger, they also increase insulin secretion in response to a meal,” Norton said. “This is in direct opposition to what the carbohydrate insulin model of obesity predicts. Based on that, GLP-1s should actually cause weight gain, not weight loss.”
He also cited studies in which the release of free fatty acids from adipose tissue was inhibited, with subjects still losing body fat without issue. His final and most pointed argument came from human randomized controlled trials.
He stated, “They tightly control food intake and equate calories and protein between diets but vary carbohydrates and fats. They show no differences in fat loss. Actually, they show a slight benefit to low-fat, higher carb diets compared to low carb, higher fat diets.”
Norton summed up by saying, “The idea that overeating doesn’t cause obesity is completely and categorically false. And he does this to push the narrative of the carb insulin model of obesity, which frankly has been debunked repeatedly. And every time it gets debunked, the people who made up the theory change it slightly so that it’s no longer debunked and they just move the goalpost a little bit.”
