Calorie counting is useless for fat loss - track carb and processed food intake instead, experts say

• Calorie counting might be an outdated approach to weight loss, according to a new review.
• Experts say hormones like insulin - and related factors like how many carbs you eat - may be driving obesity rates.
• More research is needed, but evidence suggests weight loss is determined by how much you eat vs. how much you burn.

Losing weight may be more than a simple matter of eating less and moving more, a group of nutrition scientists, experts, and doctors say.

An opinion article published September 13 in The American Journal of Clinical Nutrition suggests obesity, and resulting health issues, aren't only about how many calories people eat, but how hormones tell the body to store fat.

Researchers from multiple institutions including Harvard, Weill Cornell Medicine, and Duke University make the case that mainstream nutrition advice has misunderstood how people gain (and lose) weight based on calories alone, arguing that hormones like insulin play a key role.

Other credible nutrition science experts disagree, arguing that research doesn't support the insulin theory and multiple factors, including calories, are crucial for weight loss.

Advocates say high-carb diets are driving obesity rates

Current public health recommendations are based on the energy balance model, which is the idea that weight is gained or lost based on how much energy you consume in the form of calories from food. If you eat more than you burn off in the form of exercise and other daily activities, you'll gain weight, according to the theory (also known as calories in, calories out theory, CICO for short). To lose weight, you need to do the opposite - exercise more, eat less, or both.

An alternative approach, according to the researchers, is the carbohydrate-insulin model of obesity, which suggests that hormone levels are responsible for how we either store or burn off body fat.

For instance, a diet high in carbohydrates, particularly processed carbohydrates, can cause spikes in blood sugar, prompting the body to release insulin. Over time, high levels of insulin can make the body less sensitive to the hormone, forcing it to release more to keep blood sugar stable. The theory proposes that high insulin levels prompt the body to store more body fat, even without an excess of calories, and also disrupt hunger cues, creating a vicious cycle of metabolic disruption.

The carbohydrate-insulin model of obesity isn't new, and has been repeatedly suggested by low-carb and ketogenic diet advocates, like journalist Gary Taubes (a co-author of the recent article).

Other experts, like pediatric endocrinologist Dr. Robert Lustig, have called into question our reliance on calories in managing weight, and says other factors, like processed food, are major factors, too.

Calories are still considered king for weight loss

While insulin plays a role in fat storage, there's a lack of research showing it matters more than calorie intake. The primary objection to the theory is that if it were true, low-carb diets would be more effective for weight loss than high-carb diets, which isn't the case, research has shown.

Other evidence suggests that while processed foods and refined carbohydrates contribute to obesity, insulin levels aren't the only explanation. Factors like caloric density, ratio of carbs to other macronutrients like fat and protein, and food environment all play a role in how people eat and lose weight.

To test the theory, researchers will have to continue conducting randomized controlled trials, which are rigorous and often costly and burdensome to do, since they require strictly monitoring what participants eat and do to eliminate confounding variables.

Until then, experts still say calories are helpful unit of measurement for understanding diet, weight, and health.