What does science actually say about intermittent fasting?

The answer

Intermittent fasting (IF) triggers autophagy - cellular self-cleaning that recycles damaged components - typically beginning 12-16 hours after the last meal. A 2019 study in the New England Journal of Medicine by Mark Mattson reviewed decades of evidence showing IF improves insulin sensitivity by 20-31%, reduces inflammatory markers, and activates brain-derived neurotrophic factor (BDNF) supporting neuronal health. The 16:8 method (16 hours fasting, 8 hours eating) reduced body weight by 3-8% over 3-24 weeks in clinical trials. However, a 2024 study presented at the American Heart Association found that time-restricted eating (8-hour window) was associated with a 91% higher risk of cardiovascular death - though this observational study had significant limitations and didn't establish causation, sparking intense scientific debate.