Cortisol is often described online as the cause of everything from belly fat to exhaustion. The reality is more interesting — and less dramatic.
What cortisol does
Cortisol is a hormone made by the adrenal glands. It isn’t simply a “stress hormone”. It:
- Helps regulate blood sugar and metabolism
- Influences blood pressure
- Modulates inflammation and the immune system
- Follows a daily rhythm — highest in the morning to help you wake, lowest around midnight
During stress, cortisol rises to mobilise energy. That’s a healthy, adaptive response.
When it becomes a problem
Chronic stress can keep stress systems activated, which over time is associated with poorer sleep, higher blood pressure, and changes in appetite and fat storage. But the effects of chronic stress involve many systems, not cortisol alone.
Genuine cortisol disorders exist — Cushing’s syndrome (too much) and Addison’s disease (too little) — but they’re uncommon and need medical diagnosis.
Myths worth questioning
“Adrenal fatigue.” The idea that chronic stress “exhausts” the adrenal glands isn’t supported by evidence, and the Endocrine Society says it isn’t a real medical diagnosis. Fatigue is real, but it usually has other causes — sleep problems, depression, iron deficiency, thyroid issues, menopause — that deserve proper investigation.
“Cortisol belly.” Chronic stress may influence where fat is stored, but abdominal weight gain in midlife is driven mainly by hormonal changes, muscle loss, sleep and diet.
Cortisol-lowering supplements and tests. Saliva tests and supplements marketed to “balance” cortisol are rarely evidence-based, and some products contain ingredients that can cause harm.
What actually helps stress
- Regular exercise
- Protecting sleep
- Social connection
- Time outdoors
- Therapy, including CBT, for persistent stress or anxiety
- Reducing the load where possible
If you have persistent fatigue, unexplained weight changes, or other worrying symptoms, see a clinician rather than self-diagnosing a cortisol problem.