Diet with exercise is a tried and true prescription for weight loss, but it's often difficult to pinpoint exactly how much weight people lose using this approach. Weight loss can be highly specific to each individual and vary depending on diet modifications and amount of physical activity. The best average weight loss numbers are often self-reported.
According to the National Weight Control Registry, which tracks data on people that have lost weight through diet and exercise, weight loss ranges from 30 to 300 lbs. The average time it takes to lose weight varies from several weeks up to as many as 14 years. Almost all participants report using diet and exercise as their approach to weight loss.
Although it is difficult to pinpoint the average weight loss through diet and exercise, there are recommendations agreed upon by most health professionals. The National Heart, Blood and Lung Institute, which prescribes diet modification and daily physical activity, recommends losing weight at a rate of 1 to 2 lbs. per week. Other health professionals recommend a slower rate of 1/2 to 1 lb. per week. For someone that commits to a 20-week program, this means an average weight loss of 10 to 40 lbs.
A healthy diet and weight loss approach that creates a 250 daily calorie deficit can yield a weekly 1/2 lb. loss. A person that incorporates more exercise to burn an additional 250 calories per day, thus creating a 500 calorie daily deficit, can expect to see a 1 lb. per week loss. Weight loss can be more rapid in the beginning of a program and then taper off as the body adjusts to diet and exercise. New modifications in diet and exercise will affect the rate of weight loss.
Average weight loss does not apply to all individuals because many factors can affect the rate at which the body consumes energy. Each individual has a different metabolism that depends on body size, sex and age. This accounts for how many calories a person burns at rest. Two people that start a similar diet and exercise at the same time will experience different rates of weight loss if one person is significantly older or has less muscle mass.