Diet versus exercise in "the biggest loser" weight loss competition

Obesity experts have criticized The Biggest Loser television show for its portrayal of an unrealistic intervention that raises false expectations for weight loss. However, the magnitude of the diet and exercise intervention has not been previously quantified.

Using a validated computational model of metabolism, I quantified the diet and exercise intervention by integrating data on energy expenditure, body weight and fat mass collected during The Biggest Loser competition.

Participant body mass index, weight, and percent body fat at baseline were 48.7 ± 10.1 kg/m(2) , 144.9 ± 39.4 kg, and 49 ± 6% (mean ± SD), respectively. During the first phase of the competition when the contestants were isolated in a boot camp environment, the average rate of weight loss was 0.4 ± 0.1 kg/d and decreased to 0.19 ± 0.1 kg/d after returning home. Total weight loss was 58.2 ± 26 kg with 81.6 ± 8.4% coming from body fat. The computer simulations closely matched these data and calculated that average energy intake decreased by 65% during the first phase to 1300 kcal/d while participating in 3.1 h/d of vigorous exercise. After returning home, energy intake increased to 1900 kcal/d and vigorous exercise decreased to 1.1 h/d. Simulation of diet alone resulted in 34 kg of weight loss with 65% coming from body fat, whereas exercise alone resulted in a loss of 27 kg with 102% from fat.

The intense diet and exercise intervention during The Biggest Loser competition were not sustainable. However, a relatively modest permanent lifestyle intervention of 20% caloric restriction and 20 min/d of vigorous exercise could maintain the massive weight loss.