Prolonged fasting and very low calorie diets are known to extend lifespan and are associated with healthy metabolic ageing in animal models. A study now shows that a fasting-mimicking diet (FMD) is also effective in reducing markers and risk factors of ageing in humans. Compared with participants on an unrestricted diet (n = 43), participants on a FMD (low in calories, sugars, and protein, high in unsaturated fat; five consecutive days per month for 3 months; n = 39) had lower body weight and body fat, and reduced blood pressure and insulin-like growth factor 1 (IGF1) blood levels, without serious adverse effects. After 3 months, individuals on an unrestricted diet were switched to the FMD. A post-hoc analysis of both FMD groups (n = 71) showed that fasting decreased BMI, blood pressure, and blood levels of IGF1, glucose, triglycerides, cholesterol, and C-reactive protein, with the effects being more pronounced in people with a higher risk of disease at baseline.