While you might be focused on the numbers on the scale, your body knows how much fat you’re holding through the hormone leptin, which is secreted into your blood in proportion to your body fat. Leptin decreases your hunger levels. When the leptin levels get lower than your body wants, your body says, “Whoa.” This is when your body thinks you’re experiencing a famine.
Your body uses less energy for metabolic processes, but your cravings also spike because it wants to get those leptin levels back to the desired set point. This process can occur for up to a year, which is one of the reasons many people gain weight after a diet. Your diet might be healthy, but you might not notice you’re eating a little more while you’re on a diet (via NBC News).
According to The Healthy, another hormone that affects your set point weight is ghrelin. Your body detects when it’s running out of energy, so it triggers this hunger hormone to motivate you to eat. Leptin and ghrelin work to keep your weight where it is rather than where you want it to be so it can survive during periods of feast and famine. After all, our ancestors weren’t concerned with how they looked in a bathing suit.