I’m sure you’ve seen these headlines:
- “The Biggest Loser”: Their bodies fought to regain weight
- “The Biggest Loser” contestants gain again: Why weight keeps coming back
- ‘Biggest Loser’ contestants have slower metabolisms
They certainly caught my attention and I was excited for another opportunity to explore the science. Where are these headlines coming from? On May 2nd, an article titled “Persistent metabolic adaptation 6 years after 'The Biggest Loser' competition” was published on the website of the journal Obesity.
Who did the research? The research was supported by the National Institutes of Health (NIH). Most of the researchers were affiliated with NIH, one was affiliated with the Washington DC Veterans Affairs Medical Center and one with Towson University in Baltimore.
Who did they study? The participants were all competitors on “The Biggest Loser” television show. They had agreed to participate in a study 6 years ago when they were doing a 30-week weight loss challenge on the TV show. Of the original 16 participants, 14 agreed to be in this current study: 8 women and 6 men. When the participants started "The Biggest Loser" competition, they all had obesity. Their average starting weight was 328 pounds and they lost an average of 128 pounds. In this study, 6 years had passed since they finished "The Biggest Loser".
What did they study? The researchers were testing the resting metabolic rate (RMR) of the participants. RMR is the amount of calories that your body needs every day to maintain your current weight without adding any extra calories for exercising. Usually, the higher your body weight is, the higher your RMR is because there is more of you that requires calories or fuel. After losing weight, it is normal for RMR to decrease because there is less of you. But sometimes the RMR goes even lower than we would expect based on your body weight. This is called ‘metabolic adaptation’ and it is believed to be one of the reasons that people regain weight. The researchers were wondering if “The Biggest Loser” participants would continue to have metabolic adaptation 6 years after the competition and if the metabolic adaptation was related to weight regain
How did they try to answer their question? The researchers looked at the weight and the RMR of the participants at the end of the competition and 6 years later.
What did they find? "The Biggest Loser" participants all had lower RMRs after losing weight in the competition. Six years later, 13 of the 14 participants had regained weight; 5 of them had regained almost all of the weight they had lost. The surprising part was that the RMR of 9 of the participants did not increase even though they gained weight. The researchers also found that the subjects who had lost more weight at 6 years after the competition continued to have lower RMRs but this wasn’t surprising. Unfortunately this is one of the challenges faced by people who lose weight. One positive outcome was that 8 of the 14 patients maintained a 10% weight loss over the 6 years. While this is much less than the amount of weight they originally lost in the competition, it is a better success then we would see in most weight loss studies.
What does this mean? We already knew that metabolic adaptation happens after losing weight and it makes it hard for people to maintain their weight loss. Since they need fewer calories to maintain their new weight, they have to be very strict forever and that’s not realistic. We didn’t know that RMR would stay low even for the patients that had regained weight. This was concerning because it would be even more difficult for those people to lose weight again. This tells us that once we have been carrying large amounts of extra weight, our body wants to settle at that weight and it makes it difficult to maintain lower weights.
There is some research that suggests that people who have bariatric surgery, such as Roux-en-Y gastric bypass, do not have the same level of metabolic adaptation. Their RMR gets lower after losing weight but it doesn’t keep getting lower over time as they continue to lose weight. This might be an advantage of bariatric surgery that helps people to maintain a greater weight loss for longer than we see in non-surgical weight loss. But we’ll save that for another post on ‘Exploring the Science’.