The Biology of Regain

Your body fights weight loss through several mechanisms:

• Leptin drops — this fullness hormone plummets with fat loss, leaving you constantly hungry
• Ghrelin rises — the hunger hormone climbs and stays elevated for at least a year
• Metabolic adaptation — your body burns fewer calories for the same activities
• Food reward rises — your brain finds food more rewarding after restriction

This is not a character flaw. It is a survival system that kept your ancestors alive through famines. The trouble is, it cannot tell a famine from a diet.