Many of the commercial diet programs offer only a temporary solution to the problem. Weight can be quickly lost but program attendees often gain the weight right back, because people return to their old eating habits. Despite the fact that millions of dollars are spent each year on quick fix programs, they do not work.
Stay away from low calorie, fad diets. After a few weeks on a low calorie diet, the basal metabolic rate (the rate at which the body burns up calories) drops. At this time, the body also begins to use muscle as its energy resource. The body thinks that it is starving, so it converts to an energy storing mode. Muscle is lost and fewer calories are burned. Weight lost with low calorie diets includes water and muscle tissue along with the fat. When normal eating habits are resumed, water and fat are regained. The muscle tissue is not regained unless exercise is used to promote its development.
Very low calorie diets cause the body to become less efficient at burning fat. This causes more fat to be gained. Yo-yo dieting over time, where weight is lost and regained, makes a person fatter in the long run, instead of leaner.
Healthy, permanent fat loss results from:
Take this approach and you will be healthier, happier, and leaner.
Source: http://www.uihealthcare.com/topics/weightcontrol/weig5297.html