Rethinking a Study of the Biggest Loser

The Thinking WomanIf nothing else, we have learned in recent years that it is possible to rationalize anything. In the pandemic and in politics, we see people taking a set of facts and coming up with wildly different interpretations. Likewise in science, we have to think hard about how to make sense of new findings. With new information, old data takes on new meanings. In this last year, we’ve learned a lot about human metabolism. So this is a good time for rethinking a decade-old study of the Biggest Loser.

Kevin Hall does this in a recent perspective for Obesity.

Metabolic Adaptation

Earlier this year, Herman Pontzer and an impressive team of collaborators blew away some of the smartest people studying human metabolism with new findings. They showed that metabolic rate is remarkably constant in much of adulthood. The total amount of energy a person burns does not really change much between the age of 20 and 60. People who are more active tend to have a lower resting metabolic rate to compensate for the requirements of physical activity. So they don’t burn much more energy than people who are less active.

In Hall’s Biggest Loser study, the subjects in the study cut their calorie intakes to lose weight. They also exercised intently to try to maintain their metabolic rate. It didn’t exactly work. Despite – or perhaps because of – all that exercise, resting metabolic rates went down. They stayed down, too, even six years later.

In light of these new findings, Hall says the intense physical activity may have been responsible:

“That may have caused compensatory metabolic adaptations to substantially decrease resting metabolic rate and thereby minimize changes in total energy expenditure.”

Outrunning a Bad Diet?

So this brings us back to old debates about working out to lose weight. “You can’t outrun a bad diet” has become a cliché for explaining that workouts are not a great way to lose weight. Dietary changes tend to be necessary.

And yet, says Hall, the persons in his study who sustained the biggest increases in physical activity were the ones who regained the least weight. So physical activity seems to play a role in maintaining a lower, healthier body weight.

In the end, this remains a very complex subject and “all of this is post-hoc speculation,” as Hall is quick to say. Rationalizing what we want to believe is not good enough. We need more research, fueled by scientific curiosity, to understand more of the objective truth about how our bodies regulate our weight and metabolic health.

Click here for Hall’s perspective, here for an excellent thread to explain it further, and here for more from the New York Times.

The Thinking Woman, painting by Alexej von Jawlensky / WikiArt

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December 21, 2021