Set point theory refers to the idea that a person's weight may be pre-determined by biology and genetics. According to the theory, the body may have the ability to maintain a person's weight through metabolism. Those who subscribe to the set point theory might believe that eating and exercising are not voluntary, but are instead controlled by the body's "internal thermostat," or set point. The set point theory may be used to explain why people sometimes tend to regain the weight lost through dieting rather quickly once they return to normal eating habits.
Those who believe in the set point theory may think that metabolism levels adapt according to diet. According to the set point theory, when a person drops below their body's pre-determined weight, or set point, their metabolism may slow down to keep weight on. When a person's weight rises, their metabolism might increase to fight the weight gain. This may explain why people sometimes reach a "plateau" and cannot lose any more weight despite continued dieting. People with low set points might be underweight, while those with high set points are sometimes obese.
Genetics may play a role in the set point theory. Eye color and personality traits may be passed from parents to children through genes, and some experts believe that a person's tendency to weigh a certain amount may also be genetic. Eating habits and exercise preferences among family members are sometimes similar as well.
Some researchers believe that set points are psychological. They cite factors such as personal preference, desired clothing size, and cultural trends as influencing weight loss or gain. They sometimes theorize that when weight goes up or down, the person subconsciously adjusts their eating habits and exercise routines so that their body will return to its set point.
Other experts feel that the set point is physiological and dependent on the body's secretion of the hormones that stimulate or slow metabolism. While dieting may not necessarily affect the set point, some believe that exercise might lower it. A lower set point might make it easier for a person to lose weight.
There is typically no reliable test to determine a person's natural set point. Some people may have the ability to control their weight through moderate eating and physical activity. If a person has been dieting for an extended period of time, their metabolism may not be functioning properly. It could take a year or more of moderate diet and exercise for their body to return to the proper set point, or a healthy weight for them.