Extreme Dieting and Metabolic Adaptation: The “Biggest Loser” Dataset (Guest Post)

Let me start by stating that I am NOT a fan of the reality show, “The Biggest Loser”. The idea of sentencing obese people to 30 weeks’ hard labour and extreme food restriction under intense public scrutiny in the name of losing weight is basically torture for entertainment.

I saw some of them on a trip to southern Utah some years ago. While my husband and I were hiking in the magnificent desert of Snow Canyon State Park, these poor souls were marching along the road, heads down, sweating, panting, and really not having fun.

But was it worth it in the end? Did their strict 30-week regimen instill in them the discipline to maintain their now lean and mean bodies? Surely their metabolism had improved, and they were now fat-burning machines as a result of the 5 hour/day intense exercise.

A recent paper in the journal Obesity (Fothergill et al 2016 Persistent metabolic adaptation 6 years after “The Biggest Loser” competition”) addressed that very question. The authors conducted a very interesting study in which 14 of the 16 original “Biggest Losers” were recruited for follow-up studies on their metabolism and body composition. They had collected data from these subjects at three time points: before the competition, immediately after the competition, and 6 years after the competition.

Here are what I think are the most interesting findings of the study:

1. While the subjects did regain weight, there was a mean weight loss of about 12% of body weight, and 8 out of the 14 participants in the study (57%) maintained at least 10% weight loss over the 6 years. That’s actually a pretty great outcome compared to most weight loss programs, where most people regain all of the weight within 1 year. 10% is really important, because some metabolic parameters can greatly improve after that kind of weight loss. In other words, it’s a very meaningful and significant weight loss outcome.
2. The subjects maintained their high levels of physical activity. This is important, because….
3. ….their Resting Metabolic Rates (RMRs) dramatically decreased at the end of the competition, and did not go back up, even after 6 years of maintaining their exercise regimen. This is called “metabolic adaptation”. The more weight the subjects lost, the slower their RMRs became.
4. The most surprising finding was that metabolic adaptation did not correlate with weight regain. In other words, despite regaining weight, their RMRs remaining low, meaning that these subjects would probably have a low RMR permanently.
5. Finally, the decrease in RMR did not correlate with changes in hormones and metabolites. Much has been made about changes in the circulating levels of the hormone Leptin. By the end of the competition, plasma leptin levels dropped dramatically (from 41 ng/ml to 3 ng/ml), but by 6 years, levels were up to 28 ng/ml; not quite normal, but it was increasing. Leptin is a hormone made by adipose tissue, and is secreted to tell the brain that the body has had enough to eat (what we call a “satiety signal”). Other metabolic hormones, such as thyroid hormone, did not change from baseline, and cholesterol levels did not change.

So, to summarize, these people did maintain some weight loss, but at the cost of their resting metabolic rate. Their metabolism has been permanently altered. Or, as Dr. Yoni Freedhoff says, destroyed. http://www.weightymatters.ca/2016/05/the-lasting-damage-of-biggest-loser_3.html

This study also showed that exercise does NOT have much impact on RMR. So all that exercise did not alter their body weights’ “set point” value.

However, these subjects clearly showed that they had a tremendous amount of discipline in maintaining their exercise regimen, probably because they were under intense public scrutiny. And most of them did maintain a 10% weight loss over the long term. So perhaps “biology is NOT destiny”, and a disciplined approach to lifestyle changes really can result in sustained weight loss.

So if exercise doesn’t increase RMR, what about diet? It was expected that the RMRs would reset back to their original values once the weight was regained, but that didn’t happen. So the lowering of RMR after that kind of dramatic weight loss is persistent, and may be permanent. The implications are that the subjects would have to eat far less than the recommended 2500 calories per day in order to maintain their original degree of weight loss. You’ve heard that some subjects had an “800 calorie handicap”, meaning that they would have to consume no more than 1700 calories per day just to maintain their weight loss. That would mean that these people would literally be hungry all the time. That is the direct result of a persistently damaged metabolism.

My take on this is that is it far, far better to simply exercise and get healthy and strong no matter what your weight. The scorched earth policy of The Biggest Loser will result in some weight loss, but at the cost of a permanently damaged metabolism.

Savita is a scientist and professor in London, Ontario. When she’s not in the lab investigating the causes of diabetes, she’s in the pool trying to keep up with her Masters swim teammates, or in a nice downtown restaurant enjoying local food and craft beer.