Energy balance

Captive primates and wild primates with access to abundant, low-effort food sources (like garbage) develop obesity and metabolic abnormalities, demonstrating that energy storage capacity exists in primates when foraging costs are removed.

Your body's ability to store fat is a survival mechanism. When you reduce physical activity (like sitting at a desk) and have easy access to food, your body will store that energy as fat, just as it does in captive primates. To manage weight, you must either increase energy expenditure or restrict energy intake to match your lower activity level.