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Popular reality television program The Biggest Loser debuted on NBC in 2004 and ran there for more than ten years. In it, obese people competed with one another via strenuous physical tasks.  They also ate a diet low in calories to see who could drop their body weight by the greatest percentage. Seeing how the Biggest Loser diet plan panned out was what kept people watching.  But prior research on The Biggest Loser competitors demonstrated that recovering lost weight does not bring the metabolism back to its pre-weight loss levels. Instead, it significantly slows down after major weight reduction.1

This means that persons who have dropped a significant amount of weight must maintain an extremely low calorie consumption. One competitor on the show dropped 239 pounds and reached a weight of 191 pounds. Yet six years later, he had gained back 100 pounds of the weight he had lost.  Now he needed to eat 800 calories each day just to stay at his weight.

The Biggest Loser diet plan didn’t work like they thought it would

The Biggest Loser results can be explained and interpreted in light of an energy conservation model. According to Dr. Kevin Hall’s “constrained model of human energy expenditure,” the contestants’ metabolisms slowed down significantly as a result of the prolonged, intense physical activity they underwent. This has the effect of lowering their metabolic rate and, as a result, minimizes changes in total energy expenditure. In other words, to preserve energy balance, their bodies automatically made compensatory modifications.

In fact, the contestants who maintained the most weight loss six years after the competition actually had the most metabolism adaptation.  This is particularly interesting given that the degree of metabolism reduction at the conclusion of The Biggest Loser competition was not related to contestants’ subsequent weight regain. This shows that the change in lifestyle, namely the sharp increase in physical activity shown in those who maintained the largest weight loss, is what led to the metabolic adaption.2 For people attempting to sustain major weight loss, the compensatory mechanisms fortunately do not totally negate lifestyle adjustments, making it possible to maintain big weight loss.

What insights towards weight loss have we gained from observing The Biggest Loser weight gain ?

The studies on The Biggest Loser contestants have shown us that active weight loss with severe calorie restriction initially leads to a decrease in resting metabolic rate. However, significant increases in sustained physical activity later cause a larger and more long-lasting metabolic adaptation.

Results from the National Weight Control Registry, which was founded in 1993 to identify traits of people who successfully maintain a healthy weight, have long shown the importance of physical activity for weight control. We don’t yet understand how long-term increases in physical activity help weight loss maintenance despite the long-term compensatory decline in resting metabolic rate. According to Dr. Hall, the reason for this can be related to the way exercise reduces appetite.

But as is always the case, we need more research  to completely understand the connection between body composition, exercise, energy balance, and weight maintenance. In the meanwhile, we should continue to heed the well-researched recommendations to consume wholesome foods in moderation, stay away from processed foods, and exercise frequently in order to maintain a healthy body weight.