
Fasting for weight loss: what the evidence really shows
Intermittent fasting (time-restricted eating and plans like 5:2) can reduce daily calories by about 200–500 kcal, which supports weight loss and may improve insulin sensitivity and brain fuel via ketones. Some evidence hints at diabetes remission in type 2 diabetes under fasting regimens, and longer fasts under medical supervision may reduce inflammation and boost metabolic resilience, but long-term safety remains uncertain. The benefits largely derive from calorie reduction rather than a magic effect of fasting; eight-hour windows simply make calorie restriction easier. Downsides include headaches, fatigue, sleep disruption, potential loss of fat-free mass if exercise is skipped, and risks for those with eating disorders, pregnant or breastfeeding, or diabetes without supervision. There is no conclusive evidence that fasting extends lifespan, and a one-size-fits-all approach does not apply.



