Intermittent fasting

Intermittent fasting means limiting your eating to fixed time windows – the focus isn't on what you eat, but when. The best-known versions: 16:8 (fast for 16 hours, eat within 8 hours, for example from 12 noon to 8 pm) and 5:2 (eat normally on five days and only around 500 to 600 kcal on two days). Calorie-free drinks are allowed during the fasting period.

What does the research say? Intermittent fasting works – but mainly because people usually eat less within shorter time windows. The HELENA study by the German Cancer Research Center (2018, 150 participants) found no meaningful difference after one year between 5:2 and conventional daily calorie reduction. A one-year study from China published in the New England Journal of Medicine (2022, 139 participants) showed that 16:8 plus calorie reduction led to no more weight loss than calorie reduction alone. The frequently cited effects on cellular clean-up (autophagy) come mostly from animal studies.

Its real value lies in everyday life: if you tend to snack a lot in the evenings anyway, or just can't get on with breakfast, 16:8 gives you a simple structure without counting calories. But if you're hungry in the mornings or get grumpy while fasting, you gain nothing – and often end up making up for it in the evening.

Important: intermittent fasting is not for children and teenagers who are still growing, not for pregnant or breastfeeding women, and not for anyone who is underweight or has a history of eating disorders. People with diabetes who take insulin or blood-sugar-lowering medication should only try it in consultation with their doctor, as there's a risk of hypoglycaemia. If you notice that fasting and eating are becoming compulsive, you can get anonymous help from the eating disorders helpline of the German Federal Institute for Public Health (BIÖG, formerly BZgA) on 0221 892031.

If you give it a try: eat a balanced diet with enough protein and vegetables during your eating windows, drink plenty, listen to your body – and after four weeks, take an honest look at whether it fits your life.