Final answer:
The set-point theory suggests an individual has a genetically determined ideal body weight that the body defends against changes through compensatory energy intake and expenditure, despite not fully explaining variations in metabolic rate or environmental influences.
Step-by-step explanation:
The theory that one's level of hunger and metabolic rate generally change according to weight gain or loss is called set-point theory. Set-point theory posits that each individual has a genetically pre-determined ideal body weight, which the body strives to maintain. This maintenance is accomplished through compensatory changes in energy intake and expenditure, thus resisting significant changes from this set point.
However, it's important to note that while set-point theory provides an intuitive explanation for weight regulation, it doesn't always align with empirical evidence. Studies have shown no changes in metabolic rate between individuals who have recently lost a significant amount of weight and those who haven't (Weinsier et al., 2000). Moreover, set-point theory does not consider social and environmental influences on body weight, which can also play a significant role (Martin-Gronert & Ozanne, 2013; Speakman et al., 2011).