The study was published on Tuesday in the journal Obesity. The lead author, Kevin Hall, chief of the Integrative Physiology Section at the National Institute of Diabetes and Digestive and Kidney Diseases, and his colleagues also presented their work at the Obesity Society’s annual meeting.
Although the study is very small and must be replicated, Dr. Hall said, it is the first to assess obese people years after they lost weight with state-of-the-art methods to measure the calories they had consumed and the amount of exercise they had done.
The researchers did their measurements when the contestants were chosen, and again at six weeks, thirty weeks and six years after the contest began.
“The findings here are important,” said Rena Wing, a psychiatry professor at Brown University and a founder of the National Weight Control Registry, which includes more than 10,000 people.
The food eaten “is the key determinant of initial weight loss. And physical activity is the key to maintenance,” she said.
The study also helps explain why that might be. One consequence of weight loss among the Biggest Loser participants was a greatly slowed metabolism.
The subjects were burning an average of 500 fewer calories a day than would be expected, Dr. Hall and his colleagues found. In essence, their bodies were fighting against weight loss.
Those who kept the weight off “are countering the drop in metabolism with physical activity,” Dr. Hall said.
During the initial weight loss, the equation was different. Then, the difference between how much weight “Biggest Loser” contestants lost could be explained by the number of calories they cut from their diets. The amount of exercise did not distinguish those who lost more from those who lost less. Continue with the original article.