Overeating is not the primary cause of obesity

Almost all of us added an inch or so to our girth during the lockdown. If we’re over 70, according to prior research noted in TR, that doesn’t matter too much. But adding a bit here and there is not the same as obesity and most of us will be able to pare ourselves down when the lockdowns end.

However, statistics from the Centers for Disease Control and Prevention (CDC) show that genuine obesity affects more than 40% of American adults, placing them at higher risk for heart disease, stroke, type 2 diabetes, and certain types of cancer. The USDA’s Dietary Guidelines for Americans 2020 - 2025 further tells us that losing weight “requires adults to reduce the number of calories they get from foods and beverages and increase the amount expended through physical activity.”

This approach to weight management is based on the century-old energy balance model which states that weight gain is caused by consuming more energy than we expend. In today’s world, surrounded by highly palatable, heavily marketed, cheap processed foods, it’s easy for people to eat more calories than they need, an imbalance that is further exacerbated by today’s sedentary lifestyles. By this thinking, overeating, coupled with insufficient physical activity, is driving the obesity epidemic. On the other hand, despite decades of public health messaging exhorting people to eat less and exercise more, rates of obesity and obesity-related diseases have steadily risen.

The authors of a study published in The American Journal of Clinical Nutrition, point to fundamental flaws in the energy balance model, arguing that an alternate model, the carbohydrate-insulin model, better explains obesity and weight gain. Moreover, the carbohydrate-insulin model points the way to more effective, long-lasting weight management strategies.

According to the lead author of the new study, the energy balance model doesn’t help us understand the biological causes of weight gain:

What the researchers say: “During a growth spurt, for instance, adolescents may increase food intake by 1,000 calories a day. But does their overeating cause the growth spurt or does the growth spurt cause the adolescent to get hungry and overeat?” he asked.

In contrast to the energy balance model, the carbohydrate-insulin model makes a bold claim: overeating isn’t the main cause of obesity. Instead, the carbohydrate-insulin model lays much of the blame for the current obesity epidemic on modern dietary patterns characterized by excessive consumption of foods with a high glycemic load: in particular, processed, rapidly digestible carbohydrates. These foods cause hormonal responses that fundamentally change our metabolism, driving fat storage, weight gain, and obesity.

When we eat highly processed carbohydrates, the body increases insulin secretion and suppresses glucagon secretion. This, in turn, signals fat cells to store more calories, leaving fewer calories available to fuel muscles and other metabolically active tissues. The brain perceives that the body isn’t getting enough energy, which, in turn, leads to feelings of hunger. In addition, metabolism may slow down in the body’s attempt to conserve fuel. Thus, we tend to remain hungry, even as we continue to gain excess fat.

To understand the obesity epidemic, we need to consider not only how much we’re eating, but also how the foods we eat affect our hormones and metabolism. With its assertion that all calories are alike to the body, the energy balance model misses this critical piece of the puzzle.

While the carbohydrate-insulin model is not new—its origins date to the early 1900s—The American Journal of Clinical Nutrition perspective is the most comprehensive formulation of this model to date, authored by a team of 17 internationally recognized scientists, clinical researchers, and public health experts. Collectively, they have summarized the growing body of evidence in support of the carbohydrate-insulin model.

Adoption of the carbohydrate-insulin model over the energy-balance model has radical implications for weight management and obesity treatment. Rather than urge people to eat less, a strategy which usually doesn’t work in the long run, the carbohydrate-insulin model suggests another path that focuses more on what we eat. According to the researchers, “reducing consumption of the rapidly digestible carbohydrates that flooded the food supply during the low-fat diet era lessens the underlying drive to store body fat. As a result, people may lose weight with less hunger and struggle.”

So, what? Well, first, of course my recipes contain none of the nasty stuff so eating them will not make you obese.

The second point I would make here is that the research ignores some recent studies which have shown that obesity is largely a product of a certain number of genes. The most recent of these studies was published last month.

The two studies are not incompatible. The researchers in both blame the availability of foods rich in sugar and high-fructose corn syrup. These, plus salt, are staples in most processed foods. But those with the obesity-linked genes are far more likely to become obese.

Probably both sets of researchers are right in their approach. The DNA researchers are trying to isolate the genes in order to develop drugs which will ward off obesity. Those behind this study are pointing to the need for a change in our diet.

For more on obesity click here.