A new study of "Biggest Loser" contestants has found that exercise may be essential to keeping weight off amongst the most successful participants.
People who are genetically predisposed to type 2 diabetes and are overweight have a higher risk of developing it. Thus, uncovering reasons why some people succeed at making weight loss stick, when others don't, is important.
Kevin Hall, an American researcher at the National Institute of Diabetes and Digestive and Kidney Diseases, in Maryland, provides an answer: physical activity – and at levels much higher than recommended by most guidelines.
After looking at the main lifestyle habits of 14 Biggest Loser contestants, he found that those who were the most successful in keeping the weight off had the greatest increase in physical activity after six years.
On average, those who managed to maintain a significant weight loss incorporated 80 minutes of moderate activity or 35 minutes of intense activity into their everyday life.
The study did not separate exercise, like going to the gym, from non-exercise physical activity done throughout the day, like walking to work, in the 80 minutes a day. This means that weight loss benefits can occur with minimal amounts of effort.
Hall and his team compared seven participants who regained five pounds more than their starting weight to seven who maintained a loss of 81 pounds. The average weight loss in the 14 participants was 13 per cent of the initial weight after six years.
It was found that those maintaining a greater weight loss of 24.9 per cent had increased their physical activity levels by 160 per cent, while those who regained weight increased them by just 30 per cent or so.
Those whose weight remained stable were burning between 11 and 12.2 kcal/kg/d during physical activity, while weight regainers burned only about 8.0 kcal/kg/d by being active.
The 11 kcal/kg/d threshold for maintaining weight loss in the study corresponds to approximately 80 min of moderate physical activity or 35 min of vigorous activity daily.
UK physical activity guidelines from the Department of Health, by comparison, call for at least 150 minutes a week of moderate exercise, or 75 minutes a week of vigorous exercise for adults.
Previous research conducted by Hall suggested that nearly all participants in the reality show who experience weight regain burn around 500 fewer calories than they should.
These new findings suggest that those who kept the weight off are countering the drop in metabolism with physical activity. Further, there was no difference in energy intake between weight loss maintainers and regainers.
Although the study is very small and must be replicated, the whole message seems to be that the food eaten is the key determinant of initial weight loss and physical activity is the key to maintenance.
The findings were published in the journal Obesity.