After successfully shedding pounds, dieters often see their weight bounce back. But they may not see the same recovery in their slow metabolism.
Researchers followed 14 participants of the TV weight loss competition The biggest loser, and they found that the dramatic weight loss significantly slowed the rate at which the participants burned calories while resting. Those metabolic slowdowns, which make it harder to shed pounds, lingered for six years after the competition — even after nearly all participants had regained much of the weight lost.
The findings, published Monday in the journal obesity, suggest that the body may purposefully slow down its metabolism to regain lost pounds and maintain a weight “set point.” If the finding holds true in larger studies of dieters, it could explain why it’s so hard to keep weight off once you’ve lost weight.
“Long-term weight loss requires a vigilant struggle against sustained metabolic adaptation that acts to proportionally counteract ongoing efforts to reduce body weight,” the authors concluded.
Weight loss is known to cause metabolic changes, but researchers had little data on how long those changes might last. The researchers followed the resting metabolic rate of 14 participants from the eighth season of the TV show and compared their measurements before, immediately after and six years after the competition.
While some contestants lost hundreds of pounds over the 30-week show, the contestants lost an average of about 128 pounds. Initially, their resting metabolism was 2,607 +/-649 kilocalories per day. By the end, their average rate dropped to 1,996 +/- 358 kcal per day. And, the researchers noted, those who lost the most weight saw the biggest drops in their metabolism.
Six years later, only one of the participants weighed less than after the competition; the other 13 participants had recovered significant amounts. Five participants regained almost all or more than the weight they had lost. But despite the weight gain, their metabolism remained low, with an average of 1,903 +/- 466 kcal/day.
Based on their individual weight, the researchers estimated that the participants burned an average of ~500 fewer calories per day than would be expected for people their size.
In addition, the researchers found that the people who continued to lose the most weight over the six years also saw the greatest slowdowns in their metabolism. This, the authors speculate, suggests that these successful participants didn’t have an easier time fighting their metabolism. Instead, they may have been exceptionally determined to maintain their weight loss, perhaps due to the fact that they lost their weight in the eyes of the public.
“Of course, the extreme and public nature of this weight loss intervention makes it difficult to translate our results to more typical weight loss programs,” the authors wrote.
While most participants couldn’t keep the weight off, they still did better than most. After six years, 57 percent of the participants had maintained at least 10 percent of their weight loss. In another study, only about 20 percent of participants managed to do so after just one year.
While the findings may discourage some dieters, the authors note that studies in patients who had gastric bypass surgery failed to reveal comparable losses in metabolic rates. This, the authors speculate, might suggest that surgical intervention can reset the “set point” of body weight, a hypothesis that should be followed up in future research.
obesity2016. DOI: 10.1002/oby.21538 (About DOIs).