Stress, cortisol and metabolic health: what's happening in the body and what can you do?

The biology of stress — from brain to blood sugar

When the brain detects a threat, the HPA (hypothalamus-pituitary-adrenal) axis is activated. It leads to the release of cortisol from the adrenal glands. Cortisol mobilizes energy by increasing blood sugar, releasing fatty acids and raising blood pressure. In an emergency situation, this is lifesaving. But when stress becomes chronic, the same system becomes a metabolic strain. PMID 34518687 PMID 30312372

Chronically elevated cortisol promotes insulin resistance in several ways. It reduces muscle cell glucose uptake, increases liver glucose production and promotes fat storage, especially visceral fat around the abdomen. At the same time, muscle protein breaks down, and bone density can decrease over time. The result is a metabolic profile similar to incipient type 2 diabetes and metabolic syndrome. PMID 34518687 PMID 30312372

How chronic stress leads to abdominal obesity

One of the most visible consequences of chronic stress is increased abdominal obesity, also known as belly fat. The reason is twofold. First, cortisol promotes fat storage directly in the fat cells around the abdomen, which have more cortisol receptors than fat cells elsewhere on the body. Second, stress often increases appetite for calorie-dense foods through interactions with ghrelin, leptin, and the reward system in the brain. PMID 30312372 PMID 20385254

This is not a matter of willpower. It is a physiological response that, in an evolutionary sense, was adaptive: after a threat, the body needed to replenish energy stores quickly. But in a modern environment where the stress comes from deadlines and notifications rather than predators, the same mechanism becomes counterproductive. PMID 30312372 PMID 20385254

Stress, inflammation and the immune system

Cortisol itself is anti-inflammatory in the short term, which is why synthetic cortisol preparations are used medically against inflammation. But with chronic stress, a paradoxical state of cortisol resistance develops, where the cells become less sensitive to cortisol's anti-inflammatory signals. The result is chronic low-grade inflammation that can be measured as elevated CRP and other inflammation markers. PMID 20385254 PMID 32504499

This low-grade inflammation is a key driver of inflammaging and is associated with increased risk of cardiovascular disease, type 2 diabetes, depression and dementia. This is one of the reasons why stress management is not just about feeling good psychologically, but is a direct metabolic and immunological intervention. PMID 20385254 PMID 32504499

What actually works — evidence-based strategies

Telling a stressed person to 'relax' is rarely helpful. The most effective stress reduction strategies are concrete, measurable and integrated into everyday life. The research points to a number of measures with a documented effect on cortisol levels, blood sugar and inflammation. PMID 32504499 PMID 9428819

When should you consider measuring cortisol?

Cortisol can be measured in blood, saliva or urine, but routine measurement in otherwise healthy individuals is rarely necessary. Clinical suspicion of severe dysregulation, such as Cushing's syndrome or adrenocortical insufficiency, requires medical investigation. For most people, the symptom picture and metabolic markers are more relevant than a single cortisol measurement. PMID 9428819

More relevant parameters in practice are waist circumference, fasting blood sugar, HbA1c, blood pressure and sleep quality. If these are affected and stress is a likely contributing factor, stress reduction should be part of the plan, regardless of what a cortisol test might show. PMID 9428819