Cortisol

Cortisol is produced in the adrenal cortex and is actually a friend: it wakes you up in the morning, mobilises sugar and fat for energy under stress, dampens inflammation and keeps blood pressure and blood sugar stable. Its levels follow a daily rhythm – high in the morning, low in the evening. Cortisol only becomes a problem when it stays elevated for long periods: due to chronic stress, lack of sleep, being constantly available, worries or even excessive training without recovery.

That's when it shows its dark side. Persistently high cortisol increases appetite, especially for sweet and fatty foods – a legacy from times when stress meant running away and that took energy. It encourages fat storage around the abdomen, because visceral fat has a particularly large number of docking sites (receptors) for cortisol. It keeps blood sugar and insulin high, breaks down muscle when energy is in short supply and disrupts sleep – which in turn raises cortisol. The result is a vicious circle that many people know from stressful phases of life: more hunger, less sleep, more belly.

What lowers cortisol levels is hardly surprising, but effective: seven to nine hours of sleep at regular times, regular moderate exercise (a brisk walk lowers cortisol, a marathon raises it in the short term), daylight in the morning, screen-free breaks, breathing exercises or meditation, social contact and less caffeine in the afternoon. Very strict diets also drive cortisol up – another reason to aim for a moderate deficit.

Pathological overproduction, known as Cushing's syndrome, is rare and needs medical care; signs would include rapid weight gain around the trunk with thin arms and legs, a round face and high blood pressure. Everyday stress doesn't call for a blood test – sleep, exercise and lightening the load work more reliably than any “anti-cortisol” supplement from the internet.

Children have their own sources of stress – school, arguments, screen time until late. Fixed routines, regular bedtimes and exercise in the fresh air help them just as much as they help adults.