Social and environmental factors play large roles in the regulation of body weight. these factors are not necessarily considered in the which claims that each individual has an ideal body weight that is resistant to change.

The answer is set-point theory.

Explanation:

This theory, as the paragraph explains, states that our body weights are unikely to change unless there is an extreme change in diet or exercising habits. This way, our "set-point" resists any changes and compensates them with a difference in the energy intake and expenditure.

However, this theory has not received much support in the scientific community, as no metabolic changes were observed in subjects who suffered a considerable weight-loss.