In sedentary young men, doing intermittent aerobic exercise for two months is linked to losing weight, and this weight loss may be connected to lower levels of the stress hormone cortisol, possibly through changes in inflammation related to fat tissue.

In sedentary young adult males, performing structured sprint intervals for two months lowers cortisol levels in the blood without changing testosterone levels.

When obese men lose weight by dieting, their body doesn’t make less cortisol overall—but because they still have some fat left, the cortisol they do have is now more concentrated relative to that fat, which might trick their body into putting fat back on, especially around the belly.

When young guys burn more calories than they eat and work out hard, their stress hormone (cortisol) changes—and that’s linked to shifts in muscle and fat. But it doesn’t explain much about why people’s bodies change differently.