Benefits of intermittent fasting

Intermittent fasting is not a diet in the conventional sense — it does not prescribe what to eat, but rather a pattern of when to eat. The most studied protocols are 16:8 (sixteen hours of fasting and eight hours of eating window) and 5:2 (five days of normal eating and two of severe caloric restriction). Its popularisation in recent years was accompanied by a research base that, while still having significant gaps, offers plausible biological mechanisms for several of the observed effects.

The most documented mechanism is the improvement in insulin sensitivity. During fasting, insulin levels drop and the body progressively switches from using glucose to using fatty acids as its primary fuel. This metabolic shift, called metabolic flexibility, reduces the chronic exposure of cells to insulin, which over time improves receptor response. In people with insulin resistance or pre-diabetes, studies of 8 to 24 weeks showed significant improvements in metabolic markers.

The connection to ageing runs through autophagy, the cellular "internal cleaning" process in which cells degrade and recycle damaged or non-functional components. Animal studies showed that fasting potently activates autophagy, and the experiments that led to Yoshinori Ohsumi's 2016 Nobel Prize in Medicine illuminated the molecular mechanisms of that process. Evidence that intermittent fasting activates autophagy in humans and that this produces long-term health benefits is still preliminary, but the biological foundations are solid and justify ongoing research.