Well, I never thought I would say this, but the show The Biggest Loser has been useful for something: it has taught us some important scientific lessons about just how much, and for how long, metabolism drops after weight loss.
(I say that the show is useless otherwise for a host of reasons: It portrays unsafe, dramatic means of weight loss that are not sustainable and gives many incorrect and inappropriate messages about obesity. I could go on…)
Fourteen participants of The Biggest Loser agreed to have their metabolism measured before the weight loss program, at the end of the 30 week competition, and again 6 years later.
The study was conducted at the National Institute of Health and published in the medical journal Obesity. The baseline weight amongst these six men and eight women was 148.9kg, and they lost an average of 58kg at the end of the 30 week competition. After 6 years, most participants regained a significant proportion of the weight lost during the show, with only one person not regaining any weight, and five people having returned to their baseline weight or above.
When they measured metabolism in these people before the competition and compared it to their metabolism 6 years later, they found that on average, their metabolism burned 499 fewer calories per day, compared to what would be expected for a person of that gender, age and body composition who had not previously lost weight.
Similar to an older study I previously blogged about, this teaches us that metabolism decreases markedly after weight loss, not only due to carrying around less weight, but also due to an additional, evolutionarily designed adaptation to defend our body weight. For The Biggest Loser contestants, this means that on average, they have to eat 500 calories less, every day, than they would if they weighed the same but had not come down from a higher weight in the past. This metabolic adaptation goes on for at least six years after weight loss (based on this study) – and of course may well go on much longer, possibly indefinitely.
So how does a person handle this new lower metabolism after weight loss, to keep the weight off? We can look to the American National Weight Control Registry to learn about habits that are associated with keeping weight off – the themes are lots of activity (at least an hour a day) and lots of self monitoring – read more on this here.
If you’d like to read more about The Biggest Loser study and the individual participants, the New York Times wrote an excellent article about it, including interviews with several participants – check it out here.