Eating a very high-fat meal before exercising reduces the normal biological brake on fat breakdown in fat tissue under the skin, leading to more fatty acids being released into the bloodstream during physical activity.

Eating a high-fat meal before exercising raises levels of free fatty acids in the blood of both lean and obese men, but does not change the levels of the stress hormones epinephrine and norepinephrine in the bloodstream.

Eating a high-fat meal reduces the ability of certain receptors in fat tissue to slow down fat breakdown, and this happens directly in the fat tissue itself, not because of changes in stress hormones circulating in the blood.

In human fat cells grown in the lab, long-chain fatty acids at a specific concentration reduce the ability of certain receptors to block fat breakdown, which may explain how dietary fat promotes fat utilization at the cellular level.

During exercise, a biological signal that normally slows fat breakdown has less effect in people who are endurance-trained compared to those who are not, suggesting that training changes how fat tissue responds to this signal.

In fasted individuals exercising, fat breakdown is more strongly suppressed in obese men than in lean men due to the activity of alpha-2-adrenergic receptors.