Fasting
Fasting is not starvation. It is a deliberate metabolic intervention with decades of research behind it, from Yoshinori Ohsumi's Nobel Prize-winning work on autophagy to large-scale trials on time-restricted eating published in the New England Journal of Medicine and Cell Metabolism.
These articles cover the full spectrum of fasting protocols, from 16:8 time-restricted eating through multi-day extended fasts. Each protocol is examined for its specific metabolic effects: when autophagy actually kicks in, how fasting affects insulin sensitivity and glucose homeostasis, what happens to mTOR signaling, and which approaches have the strongest clinical evidence.
We also address the practical side that most fasting content ignores: how to combine fasting with exercise without losing muscle mass, which electrolytes you actually need during extended fasts, how fasting interacts with common medications, and who should not fast at all. The fasting mimicking diet developed by Valter Longo gets its own treatment, with a look at the clinical trial data rather than the marketing.
Every claim here is tied to specific studies. When the evidence is mixed or limited to animal models, we say so explicitly.
Go deeper
The Outlive Protocol: Fasting
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Frequently asked questions
When does autophagy actually start during a fast?
Autophagy is not a binary switch. It ramps up gradually, with meaningful upregulation beginning around 24-48 hours of fasting in humans based on available evidence. Shorter fasting windows like 16:8 may offer metabolic benefits through other mechanisms (insulin sensitivity, circadian alignment), but the autophagy claims around intermittent fasting are often overstated.
Will fasting cause muscle loss?
Short-term fasting (16-24 hours) does not cause significant muscle loss, especially if you maintain resistance training and adequate protein intake during eating windows. Extended fasts (48+ hours) do carry muscle loss risk, which can be partially mitigated by maintaining activity levels. The research suggests growth hormone increases during fasting help preserve lean mass in the short term.
Is intermittent fasting better than caloric restriction?
The evidence is mixed. Several studies, including a 2022 trial in the New England Journal of Medicine, found that time-restricted eating produced similar weight loss results to standard caloric restriction. The potential advantage of fasting lies in its metabolic effects beyond weight loss (improved insulin sensitivity, autophagy activation, and circadian alignment), though these benefits require longer fasting windows than most people practice.