The Biggest Loser was a popular reality television show that ran on NBC for over a decade starting in 2004. In it, participants with obesity competed with each other through intense physical challenges and ate a reduced-calorie diet to see who could lose the highest percentage of body weight.
Prior findings from studies of The Biggest Loser contestants showed not only that metabolism slows drastically following significant weight loss, but also that regaining the lost weight does not restore metabolism back to its pre-weight loss levels. This means people who have lost large amounts of weight must adhere to an extremely low-calorie intake in order to maintain that weight loss. One show contestant lost 239 pounds and achieved a weight of 191 pounds, yet six years later, after regaining 100 pounds of that lost weight, had to consume an 800-calorie-per-day diet to maintain his weight.
New research about physical activity and metabolic rate
A more recent study by the same researcher aims to explain and interpret the findings from The Biggest Loser in light of an energy conservation model. In what he calls the “constrained model of human energy expenditure,” Dr. Kevin Hall theorizes that because the contestants engaged in large, sustained periods of intense physical activity, their metabolisms slowed substantially in order to reduce their metabolic rates and thereby minimize changes in total energy expenditure. In other words, their bodies made automatic compensatory changes to maintain energy balance.