The 3,500 calorie rule of dieters states that since there are 3,500 calories in one pound of fat, eating 500 fewer calories per day helps to lose one pound in a week. Researchers do not accept this rule, as it does not account for the reduction in the metabolic rate, loss of muscle mass, and other factors that influence the loss of body weight. According to Researcher Kevin Hall, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), this rule is very unrealistic.
Hall and colleagues with the World Health Organization, Columbia University, and the Harvard School of Public Health have developed a web-based weight loss prediction model that can predict a dieter’s expected weight loss over a period of time, more realistically. This body weight simulator can be found in the NIDDK website. According to Hall, weight loss occurs more gradually, and cutting down 10 calories a day will help to lose one pound over three years. Reducing 250 calories will lead to a loss of 25 pounds, but that will take three years to achieve.
Half of the body weight will be lost in the first year, after which, the rate slows down. He says that this new way of analyzing the weight loss trajectory will enable people to have a more realistic view of what to expect from exercise and diet. According to the new model, although the weight loss slows down over a period of time, people who stick to the diet will continue to lose weight for a long time. To achieve the average weight similar to those in 1970s, moderately obese people would have to cut down 500 calories from their daily diet for several years.