Cortisol

Cortisol is the body's main stress hormone. Short bursts are normal and useful. The problem is chronic elevation.

In the lean context, high cortisol over weeks and months pushes the body to hold visceral fat (the deep belly fat around the organs), break down muscle for fuel, and crave sugar and salt. It also blunts recovery, which means the same training session takes longer to come back from. Bringing cortisol back to baseline is one of the most direct ways to make body composition work in your favor.

A natural cortisol pulse at sunrise is what gives the body the energy to get up and into the gym. That pulse is healthy. The damage comes from cortisol staying high through the day and into the night, a sign the nervous system never settles.

What lowers it

• Walking. A daily walk is one of the most reliable cortisol regulators most people have access to.
• Sleeping. Cortisol falls during deep sleep. Short sleep keeps it elevated through the next day.
• Stress management. Anything that brings the nervous system back to baseline lowers cortisol directly.
• Sun exposure. Morning daylight helps the cortisol pulse fire on time and fall back cleanly.

What raises it

• Alcohol. The body treats ethanol as a stressor. Cortisol runs higher through the night after drinking.