Overweight and obese women may need to exercise 55 minutes a day, five days a week in addition to low-calorie dieting in order to sustain a weight loss of 10% over two years, a study has concluded.

A minimum of 30 minutes' physical activity on most days of the week is recommended, or 150

minutes a week. However, there is a growing consensus that more exercise may be needed to enhance long-term weight loss. To calculate the amount of exercise needed, researchers from Pittsburgh University enrolled 201 overweight and obese women in a weight loss intervention. The women ate between 1200 and 1500 calories per day, and were assigned to one of four groups based on physical activity amount and intensity. After six months, women in all groups had lost an average of 8% to 10% of their initial body weight. However, most women were not able to sustain this weight loss. Women who maintained a loss of 10% or more over two years reported performing more physical activity--275 minutes per week over the baseline level of activity.

The authors conclude that the addition of 275 minutes of physical activity a week, in combination with a reduction in energy intake, is important in allowing overweight women to sustain a weight loss of more than 10%.

Jakicic JM, Marcus BH, Lang W, Janney C. Effect of exercise on 24-month weight loss maintenance in overweight women. Archives of Internal Medicine, 2008; 168(14): 1550-9.