Obese mice eat less after fasting than lean mice—even when given their favorite food—and this isn’t just because they’re heavier; it’s linked to higher levels of the fat hormone leptin.

In young, lean men, individuals with higher levels of the hormone leptin in their blood before overeating tend to gain more fat and total energy when consuming excess calories over time.

Central adiposity and metabolic dysregulation (e.g., leptin resistance) can reduce appetite and lead to decreased meal frequency, creating reverse causation in observational studies.

In mice, fat cells show increased activity of YAP/TAZ proteins when they are fed again after fasting or when fed a high-fat diet, and this activity is linked to changes in leptin levels, a hormone involved in energy balance.

In mice fed a high-fat diet, repeated cycles of losing and regaining weight were linked to less fat around internal organs and lower levels of the hormone leptin, compared to mice that did not cycle in weight, without signs of worse metabolic health.