Final answer:
The set point theory asserts that each individual has an ideal body weight that is resistant to change. It is a simple explanation of how body weight is regulated.
Step-by-step explanation:
The theory that asserts that each individual has an ideal body weight that is resistant to change is the set point theory. According to this theory, our bodies have a genetically predetermined set point for weight, and efforts to significantly change our weight are resisted by compensatory changes in energy intake and/or expenditure. While the set point theory has limitations and does not account for social and environmental factors, it is still used as a simple explanation of how body weight is regulated.