It is a question that plagues all who struggle with weight: Why do some of us manage to keep off lost pounds, while others regain them?

Now, a study of 14 participants from the “Biggest Loser” television show provides an answer: physical activity — and much more of it than public health guidelines suggest.

On average, those who managed to maintain a significant weight loss had 80 minutes a day of moderate activity, like walking, or 35 minutes a day of vigorous exercise, like running.

The researchers conducting the new study did not distinguish between purposeful exercise, like going to the gym and working out, and exercise done over the course of the day, like walking to work or taking the stairs.