So easy to lose but so easy to put back on

Blame your biology. When you gain weight, your body produces more fat cells that are larger in size, says Randy Seeley, of the University of Michigan School of Medicine.

This process also increases your levels of leptin, a hormone that regulates fat storage. In short, your body adapts to carrying fat. But when you lose weight, your leptin levels fall. “Your brain sees that as a problem and that you’re starving to death,” Seeley says. In turn, you’re hungrier more often and find it harder to fight off cravings.

Lower leptin levels have another effect: Reduced amounts of the hormone encourage your body to burn fewer calories. So you not only want to eat more often but also have a harder time burning calories. Research shows that it’s extremely difficult to adapt to a lower weight as well as the reduced size and number of fat cells.