The set point is the theoretically preferred level at which an individual’s weight or other physiological variable is regulated. Homeostatic mechanisms are thought to defend this level by adjusting appetite and metabolism.

When body weight falls below the set point, hunger increases and metabolic rate may decrease, promoting weight regain. When weight rises above the set point, appetite may diminish and metabolism may increase. The concept helps explain why many people regain lost weight after dieting: the regulatory system treats the lower weight as a deviation to be corrected. Twin and adoption studies suggest that the set point itself is partly heritable.

The simple set-point model has been refined. Some researchers prefer a settling-point account in which weight stabilizes at the balance of multiple factors rather than being actively defended around a fixed target. Environmental changes—caloric density of food, physical activity levels—can shift the level at which weight stabilizes. Nonetheless, the idea of a defended body-weight range remains influential in obesity research and clinical practice.

The body appears to treat certain weight levels as targets to be maintained.