How exercise affects metabolism and weight loss

Many of us remember Lose to Win (The Biggest Loser), the popular regular reality show that ran for over a decade starting in 2004, as The contestants competed vigorously to lose a ton of weight in a short period of time. One of the biggest lessons of the broadcast seemed to be that intense exercise, combined with strict calorie restriction, resulted in significant weight loss.

However, media coverage of the contestants years later seems to tell a different story, about weight gain back, a slower metabolism, and the futility of trying to lose weight in the long term.

right Now, A new scientific analysis of the program and its effects was published last month in the journal obesity, suggests that many beliefs about “lose to win” may be wrong. The analysis attempts to reveal what actually happened to the participants’ metabolism and why some withstood better than others. It also examines the complex role of exercise and whether staying physically active has helped runners keep their weight in check for years.

For those who may have forgotten, or tried, “Lose to Win” was broadcast on the network. NBC With high levels of general audience for more than 12 seasons. Participants competed to lose the most kilograms by using severe calorie restrictions and hours of strenuous exercise each day. in general, The “winners” lost dozens of kilograms in a few months.

Rapid and intense weight loss has caught the attention of Kevin Hall, a senior researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, part of the National Institutes of Health. As a metabolic expert, Hall recognized that when people lose a lot of weight in a short time, they often send off their weight. metabolic rate At rest (the basic calories we burn each day once we are alive) in free fall. A lower resting metabolic rate may mean we burn fewer calories overall.

This effect was previously thought to be due in part to muscle loss during the diet. Being a relatively active tissue, muscle burns more calories than fat, and more muscle overall means a higher metabolic rate. So Hall wondered: Did rampant levels of exercise during “win-loss” help dieters preserve their muscle tissue and keep their resting metabolic rate at a high level, even when they lowered their calorie intake?

For more than a decade, Hall and his colleagues began the first series of experiments to find out. In a 2012 study, they compared 16 men and women who lost a lot of weight by cutting calories, thanks to gastric bypass surgery, and 16 contestants in a Lost to Win program whose extreme weight loss included exercise and diet. As expected, the bypass group lost muscle and fat, while participants in the “loss to win” program retained most of their muscle tissue and lost primarily fat. However, their resting metabolic rate dropped to about the same amount, regardless of whether or not they were keeping some good muscle.

Hall said he and his colleagues were surprised by the results. Furthermore, their confusion intensified when, in a 2016 study, they retested 14 of the same runners six years after their competition and expected to see that their metabolism had rebounded by then. The resting metabolic rate of most dieters rises slightly after they stop actively losing weight, especially if they regain a few kilograms. Larger people burn more core calories than smaller people. By that date, most runners have gained weight. However, their resting metabolism was still sluggish, and they burned an average of 500 fewer calories per day than they had before they appeared on the show.

The following year, a follow-up study concluded that Physical activity has helped some runners avoid gaining weight. If they moved or exercised for about 80 minutes almost every day, they regained fewer kilos than if they exercised on a few occasions.. However, his physical activity did not stimulate his metabolism at rest. Those who exercised, in fact, showed the greatest reduction in terms of resting metabolic rate.

Perplexed, Hall recently began revisiting “loss to win” studies in light of a new conception of how fundamentally human metabolism works. This idea came from an influential 2012 study showing that highly active hunters in Tanzania burn the same relative amount of calories per day as the rest of us, even when they move a lot.

Scientists involved in this research hypothesized that tribal peoples’ bodies should automatically compensate for some of the calories they burned while foraging by reducing other physiological activities, such as growth. (Tribesians tended to be short.) In this way, the researchers believe that hunters’ bodies can keep the total number of calories they burn each day in check, no matter how many kilometers they search for tubers and prey. Scientists called this idea Limited Total Energy Expenditure Theory.

Recognizing this research, Hall began to see potential similarities in the “loss to win” outcomes. So for the new analysis, he went back to reviewing his group’s data for clues about whether the runners’ metabolism behaved, in practice, like that of hunting and gathering. He’s found clues in resting metabolic rates. Hall noted that the numbers plummeted early in the “Lose to Win” shoot, when they reduced how much they ate, so it’s understandable that their bodies reduced the calories they burned to avoid starvation..

However, in subsequent years, When the contestants went back to eating the way they did before, their metabolism remained depressed because, Hall concluded (and that was the key), most of them were still exercising.. Paradoxically, he wrote in the new analysis, Repetitive physical activity appears to instruct your body to keep your resting metabolic rate low, so that your total daily energy expenditure can be reduced..

It’s still just a hypothesis, but it seems that what we’re looking for” in the “loss to win” data is “an example of a finite energy model,” Hall said.

So what might this rethinking of the “loss to win” story mean for the rest of us, if we hope to keep our weight in check? Hall said that the first and most important thing is that he indicates it Sudden and massive weight loss will generally rebound, as this strategy appears to send your resting metabolic rate more than expected, given people’s smaller body sizes. He noted that when people lose weight gradually in weight-loss experiences, their metabolic changes tend to be less severe..

The second and most puzzling thing is, If you’ve lost a significant amount of weight, in the “lose to gain” style, exercise is likely an ally and something that sabotages your efforts to avoid gaining those pounds back.. In Hall’s new interpretation of long-term weight control in the runners, repetitive exercise kept the participants’ resting metabolic rate low, But it also helped them avoid gaining fat again. content, Competitors who exercised more ended up gaining less weight, although their relative metabolism was also slower..

It’s unclear exactly how and when exercise helped them maintain their weight, Hall said. You suspected that exercise affected people’s appetites in ways that might make them less likely to overeat, while also burning a few extra calories.. He said he hopes to develop future trials to find out how exercise affects metabolism, through thick and thin.

So far, that may be the most poignant lesson of ‘lose to win’ Losing weight in the long term, although daunting, is not useless. Yes, most Lose to Win contestants gained weight again, Hall said, but not necessarily every pound they lost. Six years later, most of them weighed about 12 percent less than they did before participating in the program, which is a big difference.The most successful previous participants were those who still exercised.

© New York Times 2021