Overeating alone doesn’t explain the obesity epidemic. There’s more to it than just ‘calories in, calories out’

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The prevalence of obesity in the United States is over 40% at the moment, up from 30% two decades ago, with severe obesity doubling during the same time. According to conventional fitness wisdom, this must mean that Americans are eating too many calories and aren’t exercising nearly enough. While there is some truth to this century-old model of weight loss, researchers now claim that calorie management and exercise — although important — have been grossly overestimated. Instead, what we eat, rather than how much we eat, may actually be more important to consider when forging an effective weight loss strategy.

“The conventional approach to weight control, based on the Energy Balance Model (“eat less and move more”) has utterly failed to stem the rapidly rising prevalence of obesity and related diseases. This failure is often attributed to the difficulty most people have controlling their eating and physical activity behaviors in the modern environment,” Dr. David Ludwig, an endocrinologist at the Boston Children’s Hospital and Professor at Harvard Medical School, told ZME Science.

“Our paper proposes that the problem arises not from such personal deficiencies per se, but rather from a fundamental flaw in how obesity is conceptualized. We argue that the Energy Balance Model simply restates a law of physics, and lacks a focus on underlying causes, and on what’s driving the obesity pandemic,” Ludwig added.

In nutrition, energy balance is the balance of calories consumed through eating and drinking compared to calories burned through physical activity. What you eat and drink is energy in and what you burn through physical activity and your metabolism is energy out. If the number of calories in and calories out cancel each other out, your weight should stay the same, per this model.

But in their new study, Ludwig and colleagues performed a major review of the existing scientific literature and found fundamental flaws in the energy balance model, which could explain failures in policies and management strategies for public health.

Instead, they propose a potentially more reliable model known as the carbohydrate-insulin model. Rather than the broad number of calories, this model explains the obesity epidemic by virtue of intake of foods with a high glycemic load, particularly rapidly digestible carbohydrates.

These highly processed carbohydrates, which include foods such as white bread, white rice, white potato, cookies, chips, and sugary beverages, increase insulin secretion and suppress glucagon secretion. This hormonal response instructs fat cells to store more calories, which leaves fewer calories available to fuel work by muscles and other metabolic activities.

To the brain, it makes no difference that you’re stuffed with calories if the body isn’t getting enough energy. If there aren’t enough calories for metabolic activities, the brain will cause feelings of hunger even though you may gain excess fat. Since we tend to remain hungry when consuming processed foods, we’ll likely consume more calories.

The new study, which involved more than a dozen international leading scientists in their fields, has summarized a huge body of evidence supporting the carbohydrate-insulin model, with massive implications for weight management and obesity treatment.

If this model is validated by research in the future, it could lead to strategies that urge people to, first and foremost, change which foods they eat rather than recommending eating less.

“If the model is substantially right, it has major implications to obesity prevention and treatment. It means that a focus on what you eat, rather than how much, could be more effective over the long term. Reducing processed carbohydrates, rather than restricting total calories, may make healthy weight maintenance easier,” Ludwig said.

Instead of processed carbohydrates, people are advised to switch to healthy high-fat foods such as nuts and nut butters, avocado, full-fat dairy, and olive oil.

“With this first step, slowly digesting carbohydrates would still be fine (whole fruits, legumes, minimally processed grains, non-starchy vegetables). For people with more severe insulin resistance, such as type 2 diabetes, more strict restriction of total carbohydrates may be ideal,” the scientist advised.

Findings appeared in The American Journal of Clinical Nutrition.

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