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11-28-17

Physical activity key to keeping weight off

More than two of every three adults nationwide are overweight or obese. Excess weight raises your risk of developing serious health problems, including heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.

A healthy eating plan and regular physical activity help you lose weight. However, maintaining lost weight is difficult for many people. Body weight reflects a complicated balance between the amount of energy consumed (calories) and the amount of energy used by the body. Researchers have been working to understand which aspects of diet and physical activity are most important for weight control.

A team led by Dr. Kevin D. Hall of NIH's National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) studied participants in a season of "The Biggest Loser," a televised weight loss competition. Of 16 competitors enrolled, 14 participated in a follow-up study 6 years later. After losing an average of about 132 pounds during an intensive 30-week diet and exercise period, many of the participants regained a substantial amount of weight after the program was over. But there was great variation among them.

The researchers explored how physical activity and energy intake were related to weight maintenance. At the beginning, week 6, and week 30 of the competition, as well as 6 years afterward, the team measured the participants' body fat, total energy expenditure, and resting metabolic rate-the energy burned during inactivity. To calculate each participant's level of physical activity, the scientists subtracted the resting metabolic rate from the total energy expenditure. They determined the calorie intake by using the observed weight and body fat changes along with the total energy expenditure measurements. Results appeared in the November 2017 issue of Obesity.

Six years after the competition, seven participants had maintained an average weight loss of about 25 percent of their starting weight. The other seven returned to a weight that was within 1 percent of their starting weight. The calorie intake of both groups was similarly reduced from before the competition began. The main difference was in levels of physical activity. The weight loss maintainers increased their physical activity by an average of 160 percent from before the competition began, while those who regained their weight had only a 34 percent increase.

The scientists calculated that an increase of about 80 minutes per day of moderate physical activity or 35 minutes per day of vigorous activity was necessary to maintain lost weight. These amounts are much greater than current recommendations for daily physical activity.

"Although this was a small study, it is the first to use accurate and objective measurements of calorie intake and overall physical activity before, during weight loss, and many years afterwards," Hall says. "Our findings are consistent with other studies in which participants who kept their weight off reported significantly more physical activity than those who regained their weight."

-by Harrison Wein, Ph.D.

For further information on this and other health topics, visit the web site of the National Institute of Health at www.nih.gov.