Diets in general make you more efficient at storing calories in your fat cells. As already mentioned above, but because it is so important, diets slow down your metabolism, making it more difficult to lose weight and easier to gain. Also, muscle mass is used for energy on a diet. The less muscle and the more fat is on your body, the lower is your metabolism and caloric needs. The result - you need less calories to maintain your weight, and you gain weight twice as quickly.
Diets are negative, restricting, and depriving.
You always crave and overeat those foods you restrict. Diets are limited in essential nutrients and certain food groups. Diets create a negative self-image. Remember - you are not a failure, the diet is a failure . As you can see, people who diet often can lower their metabolisms enough to decrease their caloric needs.