Definition: The set point theory suggests that each person has an established, normal body weight, a metabolic thermostat that regulates our body fat and weight. Some people have a high setting some people have a low setting, with the body pulling you back to your set point weight, which might explain why some people gain weight back after losing it.
However, whether this theory is true or not is in question. One study found no evidence that set point weight is the reason some people gain weight after losing it.
Sources:
Weinsier, R; Nagy, T; Hunter, G; et al. Do adaptive changes in metabolic rate favor weight regain in weight-reduced individuals? An examination of the set-point theory. Am J Clin Nutr, 2000 Nov;72(5):1088-1094.
