In response to mental stress, men tend to have a higher peak cortisol level than women, with a 25–30% greater increase. In contrast, women tend to have a stronger cortisol response to eating a midday meal after exercising, especially when caffeine has been consumed.

After exercising and eating lunch, women tend to have higher cortisol levels than men, and this difference becomes larger if they consumed caffeine beforehand.

In healthy adults, doing moderate exercise by itself does not raise cortisol levels much, but when caffeine is consumed before exercise, cortisol levels rise about 40 minutes after the workout in both men and women.

Consuming 750 mg of caffeine daily in three doses increases cortisol levels throughout the day when individuals are exposed to mental stress, physical exercise, or eating after exercise, and this increase occurs similarly in both men and women, though the overall stress response size may differ by sex.

Consuming caffeine before a mentally stressful task leads to a 15–20% higher increase in cortisol levels compared to taking a placebo, and this effect is similar in men and women.

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.