The American College of Sports Medicine has released a new position stand called Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults. Here is a summary. Note the recommendation for strength training, which is so important for lean body mass (muscle and bone) maintenance.

◆Prevent weight gain
*150-250 minutes/week of moderate-intensity physical activity is associated with prevention of weight gain.
*More than 150 minutes/week of moderate-intensity physical activity is associated with modest weight loss.

◆Weight loss
*150-250 minutes/week of moderate-intensity physical activity provides only modest weight loss.
*Greater amounts (eg, >250 minutes) provide clinically significant weight loss.
*Energy/diet restriction combined with physical activity will increase weight loss as compared to diet alone.

◆For weight maintenance after weight loss
*There is some evidence that >250 minutes/week of moderate-intensity physical activity will prevent weight re-gain.

ACSM recommends that adults participate in at least 150 minutes/week of moderate-intensity physical activity to prevent significant weight gain and reduce associated chronic disease risk factors. For most adults, this amount of physical activity can be easily achieved in 30 minutes/day, five days a week. Overweight and obese individuals will most likely experience greater weight reduction and prevent weight regain with 250+ minutes/week of moderate-intensity physical activity. ACSM also recommends strength training as part of this health and fitness regimen, in order to increase fat-free mass and further reduce health risks.

DONNELLY, JOSEPH E. Ed.D (Chair); BLAIR, STEVEN N. PED; JAKICIC, JOHN M. Ph.D.; MANORE, MELINDA M. Ph.D., R.D.; RANKIN, JANET W. Ph.D.; SMITH, BRYAN K. Ph.D.
Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults.[SPECIAL COMMUNICATIONS: Position Stand].Medicine & Science in Sports & Exercise:Volume 41(2)February 2009pp 459-471.