Cortisol

At a Glance

What is cortisol?

Cortisol is a glucocorticoid, which means a steroid hormone involved in metabolism, inflammation, and the body’s response to stress. It is made by the adrenal glands, which sit above the kidneys. It can be measured in blood, urine, or saliva.1

Cortisol is released through the HPA axis. HPA means hypothalamic–pituitary–adrenal. In simple terms, the brain signals the pituitary gland, the pituitary signals the adrenal glands, and the adrenal glands release cortisol.

Cortisol also follows a daily rhythm. In most people with a regular sleep schedule, levels rise before waking and usually peak within about 30 to 60 minutes after waking. This is called the cortisol awakening response.2

What the Evidence Says

1. Clinical high cortisol is different from being stressed

Cushing syndrome is the clearest example of harmful cortisol excess. It can happen because the body makes too much cortisol, or because a person has taken glucocorticoid medicines such as prednisone or dexamethasone for long enough to cause cortisol-like effects. The clinical pattern is not just “feeling stressed”. It is usually progressive and includes features such as central weight gain, rounded face, fat at the upper back, skin thinning, easy bruising, wide purple stretch marks, muscle weakness, high blood pressure, diabetes, and low bone density.414

Guidelines recommend testing for Cushing syndrome when people have multiple, progressive, or unusual features, especially features that are more specific for cortisol excess. Recommended first-line tests include 24-hour urinary free cortisol, late-night salivary cortisol, and the 1 mg overnight dexamethasone suppression test. Random serum cortisol is specifically not recommended as a screening test.13

2. The belly-fat claim is biologically plausible, but often exaggerated

There are plausible mechanisms. Cortisol can affect appetite, glucose metabolism, fat storage, and local cortisol activity in adipose tissue. Reviews of stress and obesity describe a two-way relationship: chronic stress may contribute to obesity risk, and obesity itself may alter stress biology.5

The problem is that real-life human studies are messy. A systematic review of obesity and HPA-axis activity found a general pattern linking abdominal fat with higher HPA-axis responsiveness, but also found inconsistent results across methods and studies.6 Hair-cortisol reviews suggest long-term cortisol exposure is more related to abdominal obesity than single blood or saliva samples, but this still does not prove that cortisol is the main cause of belly fat in an individual person.7

3. Lowering cortisol is not the same as losing belly fat

Stress management can change cortisol markers. In a 2024 systematic review and meta-analysis, stress management interventions outperformed control conditions for cortisol, with mindfulness, meditation, and relaxation among the more effective categories.8 Exercise may also help, especially mind–body practices such as yoga and qigong in adults with psychological distress.9

But this is not proof of targeted belly-fat loss. A lower cortisol value does not automatically mean fat loss, and fat loss depends on energy balance, sleep, diet, physical activity, medicines, medical conditions, and genetics. The strongest practical advice is to treat stress reduction as part of general metabolic health, not as a spot-reduction trick.

4. Ashwagandha is not a cortisol detox

Ashwagandha has more evidence than most “cortisol support” supplements, but the evidence is still limited. A 2025 systematic review and meta-analysis reported lower measured cortisol in randomized trials, while also noting uncertainty around perceived stress effects.10 Official safety sources caution that long-term safety is not known and that ashwagandha may interact with medicines, affect thyroid function, and rarely be linked with liver injury.1112

Are Results Consistent Across Studies?

Why We Rate It This Way

Safety Note

Do not stop prescription steroids suddenly. Prednisone, dexamethasone, hydrocortisone, inhaled steroids, topical steroids, and steroid injections can affect the HPA axis. Stopping suddenly can be dangerous, especially after longer use.

Be cautious with ashwagandha. Official sources advise avoiding it during pregnancy and breastfeeding, and caution in people with thyroid disorders, autoimmune disease, liver disease, hormone-sensitive prostate cancer, or use of sedatives, thyroid medicines, blood pressure medicines, diabetes medicines, anticonvulsants, or immunosuppressants.1112

What This Means For You

What We Still Do Not Know

We still do not know which stress-reduction programs meaningfully improve long-term metabolic outcomes through cortisol specifically. Many studies measure cortisol but not abdominal fat, and many measure stress or fat but not cortisol carefully.

We also need better long-term safety and effectiveness data for ashwagandha, including independent trials using standardised products, larger sample sizes, longer follow-up, active safety monitoring, and clearer reporting of conflicts of interest.

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