The journal Obesity has published a fascinating paper on what has to be the most popular weight loss experiment of all time, The Biggest Loser. The paper, by Dr. Kevin Hall, et al., found that all but one of the contestants gained back a significant amount of weight and several had higher weights at year 6 than they did at baseline. So most people who lose a lot of weight gain it back, is that really a surprise?
Perhaps not, but the surprising result in BL participants was the long-term change in their metabolic rate. Namely, even participants who gained back all of the weight they lost had significantly lower metabolisms even 6 years after their initial weight loss. On average, participants burned 500 fewer kcals/day than would be predicted for a person of their height and weight. What does this mean? It seems that BL alumni will have to permanently restrict their energy intake simply to maintain their current weight.
Researchers noted that:
“…’The Biggest Loser’ participants with the greatest weight loss at the end of the competition also experienced the greatest slowing of RMR at that time. Similarly, those who were most successful at maintaining lost weight after 6 years also experienced greater ongoing metabolic slowing.”
If BL contestants, who are arguably highly motivated to maintain weight loss both during and after filming – since many make their livings as spokespeople or fitness instructors after leaving the show – experience these effects, is there any hope for normal dieters?
However, weight regain isn’t just a matter of altered metabolic rate; various hormones are altered in weight loss. In the Biggest Loser study, Hall et al noted that participants had significantly lower levels of leptin, a hormone usually proportional to fat mass that suppresses appetite and causes decreased energy intake.
Obesity doctor, Yoni Freedhoff, reflected on the patients in his clinic who had sustained significant weight loss. Noting that “losing 40-50% of presenting weight” is not common in his office, he adds. “I can think of 3 patients who have lost >40% of their presenting weights with our office, and I don’t recall any having metabolic slowdowns [measured via indirect calorimetry] beyond what would be expected from losing [weight].”
And losing >40% of body weight is not always advisable. The CDC reports that patients with overweight can experience significant health benefits by reducing weight by as little as 5%.
For some reason, it seems participants of BL have a uniquely slowed metabolism that don’t provide a good model for normal weight loss. This is consistent with Hall’s 2014 paper showing that Biggest Loser participants showed greater metabolic adaptation than matched study participants who underwent Roux en Y gastric bypass. For that reason, perhaps the BL studies, while fascinating, shouldn’t be extrapolated to all weight loss efforts.
It's highly likely that weight loss will continue to be a recommended course of action for patients with obesity or weight related chronic diseases. But, as the CDC says, weight loss should be focused on the amount of weight necessary for improving health outcomes and dieters don't need to go to extremes to make manageable, healthy changes.
Have you read the NYT coverage and want to learn more? Other recent BL articles: