From a position stand by the American College of Sports Medicine
ACSM recommends that the public follow these general guidelines for losing weight and keeping it off: Consult with a trained healthcare professional, consider losing weight if BMI is 25 or above, reduce caloric and fat intake, exercise 2.5 - 4.5 hours a week, and use dietary supplements/weight loss drugs only under physician supervision.
-An "energy deficit" of 500-1000 calories a day is recommended
-An effective weight-loss program must include increased energy expenditure in addition to reduced dietary intake.
-Significant health benefits can be realized with a minimum of 150 minutes of moderate intensity exercise a week; there may be advantages to increasing to 200-300 minutes per week
-Even modest reduction of 5-10% produce significant health benefits
-If energy needs exceed energy intake, weight loss will occur
-Very low calorie diets (VLCDs), used in conjunction with dietary supplements and requiring medical supervision, may increase the magnitude and rate of weight loss but probably will not improve long-term weight loss