opinion | Carbs, not calories, may be responsible for obesity


David S Ludwig He is associate director of the New Balance Foundation’s Obesity Prevention Center at Boston Children’s Hospital, professor of pediatrics at Harvard Medical School, and professor of nutrition at Harvard T.H. Chan School of Public Health.

The usual way to understand obesity is simple: If you consume more calories than you need to fuel yourself, the excess is deposited in body fat and you gain weight. Because, according to this approach, All calories are the same For the body, the only way to lose weight is to eat less of it or burn more exercise.

For a century, the idea of ​​”energy balance” has dominated the prevention and treatment of obesity, beginning with the original focus on Calorie Calculator In the early twentieth century, to Low fat diet (targeting the most energy-dense nutrients) in the late twentieth century, to a recent focus on reducing the consumption of Modern processed foods High in fat and sugar.

If this theory is correct, it is difficult to agree with the facts. After more than three decades of increase, calorie consumption in the United States has decreased or decreased since 2000, New analysis concludes. But obesity rates have increased by more than a third since then, reaching 42% of the population today. This discrepancy cannot be explained simply by our sedentary lifestyles—in fact, Americans have become somewhat more physically active over the past 20 years.

So what if the focus on calories and energy balance was simply wrong, reversing cause and effect? write in European Journal of Clinical Nutrition This week, the authors shared with me – researchers, clinicians, and public health experts – my argument that overeating is not the main cause of obesity. Instead, the process of gaining weight leads to overeating.

This is a different form of obesity, The carbohydrate and insulin model. This theory blames high levels of obesity on the processed, fast-digesting carbohydrates that flooded our diets during the low-fat diet craze — white bread, white rice, ready-made breakfast cereals, potato products, and sugary foods. It is assumed that consuming these carbohydrates significantly raises insulin levels and produces other hormonal changes that program our bodies to store excess fat.

Seen in this way, obesity is not a problem of overeating, it is a problem of calorie distribution – too many calories from each meal are absorbed into fatty tissue and too few into the blood to satisfy the body’s energy needs. Thus, our brains make us feel hungry faster after eating to make up for those trapped calories. If we try to ignore hunger and restrict calories, the body conserves energy by slowing down the metabolism. In this sense, obesity is a state of starvation amid abundance.

According to this theory, simply reducing calories does not work in the long term, because it does not address the underlying predisposition to excess fat storage driven by hormones and other biological influences. Instead, the focus should be on reducing the rise in blood glucose and insulin after meals that contain a diet high in fat and low in processed carbohydrates. In this way, adipose tissue can be persuaded to excrete pent-up calories, resulting in reduced hunger. Weight loss occurs without the need for calorie restriction, which increases the likelihood of long-term success.

So is the carbohydrate and insulin model more valid than energy balance thinking? Unfortunately, we still don’t know for sure. The definitive research needed to resolve this controversy has not been done, in part because alternative models of obesity have not been taken seriously.

two scientific Leaves, in addition to the new model we did this week, aims to build the carbohydrate-insulin model from the available scientific evidence. However, there were more than dozen Leaves From critics claim Refutation of the model based on weak evidence, such as small, short-term trials of two weeks or less.

In the meantime, although investing in many pioneer low fat Diet trials (nearly all of them fail to show any benefit for the main results), the government’s National Institutes of Health did not fund a single long-term low-carbohydrate trial of a similar scope. This wasn’t a fair contest for ideas.

One reason for this resistance may be cultural. For centuries, obesity was viewed as a character defect. Despite decades of research into genetic and biological influences In terms of body weight, obese people are still more stigmatized than those with almost any other chronic disease, as if their weight was their fault.

Thinking about energy balance implicitly contributes to these stereotypes by blaming overeating on poor self-control. despite Energy Balance latest releases Emphasis on the primary reward centers in the brain that drive food intake, and in both cases, obese people are considered unable to resist tempting foods for conscious or unconscious reasons. If the alternative model is correct, then deeply ingrained notions about obesity are simply wrong.

Scientists are supposed to be skeptical. But when variations of the same approach continue to fail—and obesity rates continue to rise—it is critical that new ideas are encouraged, not suppressed. And at a cost of one doubling associated with weight, type 2 diabetes, roughly 1 billion dollars a dayWe should think of different ways to solve the stubborn problem of obesity and open our minds to a seemingly extreme idea: overeating is a symptom, not a cause.