Participants in the TV reality show “The Biggest Loser” regained over six years much of the weight they had lost in the competition because of persistently slow metabolisms, according to a study that followed the contestants. The study, published in the journal Obesity, helps to explain why losing weight — and maintaining a new and lower weight — might be so difficult.
The National Institute of Diabetes and Digestive and Kidney Diseases study, “Persistent metabolic adaptation 6 years after “The Biggest Loser” competition,“ measured resting metabolic rates and metabolic adaptation to offers insights into why all but one of the “Biggest Loser” participants significantly regained weight, on average 41 kilograms (90 pounds), in subsequent years. Researchers followed 14 of the U.S. show’s 16 contestants.
Participants’ resting metabolic rate turned out to stay at the same level as at the competition’s end, while their metabolic adaptation was continuously dropping. This means that, compared to a person of the same age and size who did not rapidly lose weight, the contestants had to consume about 500 fewer calories per day to refrain from gaining weight.
Metabolic adaptation is a process that counteracts weight loss by decreasing energy consumption, in essence slowing metabolism. Nevertheless, the most successful contestants also had the largest decreases in resting metabolic rate at the show’s close. Individuals who best managed to maintain their weight loss after six years also had slowing metabolisms, and the study’s authors suggested that metabolic adaptation is a proportional, but incomplete, response to weight loss from a pre-set value.
An earlier study found that patients who undergo gastric bypass weight loss surgery do not experience a decreasing metabolic adaptation, suggesting that their body-weight set point is somehow permanently reset.
The study, the first of its kind to follow weight-loss participants for such a long time, also attempted to tease out metabolic changes that might be associated with the metabolic slowing. But it could not associate any hormones or metabolites to this change — a result that might be explained by the low numbers of study subjects. The authors also noted that other factors, not measured in the study, might better explain this metabolic shift.