The set-point model of body weight regulation, involving coordinated changes in appetite and energy expenditure to defend a specific weight range, provides a better explanation of human weight dynamics than static or settling-point models.

When body fat decreases, fat cells release less leptin, which tells the brain to increase hunger and slow down calorie burning. The brain responds by making a person feel hungrier and burning fewer calories at rest, pushing the body back to its original weight. When body fat increases, leptin rises and does the opposite — reducing hunger and increasing calorie burning to prevent further gain.