Is fasting beneficial for longevity?

Key Points

• Fasting’s longevity benefits in humans remain uncertain. Fasting and caloric restriction have extended lifespan in model organisms, but there is no clear evidence establishing an effective human protocol. Long-term studies would be difficult, and researchers lack reliable biomarkers for many aging-related cellular processes.
• There is no established “right” protocol. The main variables are how long to fast, how much to restrict intake, and how often to repeat the fast. Attia said his past regimen was based on his own reasoning, not evidence that it was optimal.
• Attia’s former fasting regimen consisted of 7–10 days of water-only fasting once a quarter, alternating with three-day fasts once a month. He stopped around 2021 after noticing substantial muscle loss over several years and difficulty regaining it. Fasting also became less appealing when he was home with his family.
• Fasting may have downsides. Attia noted that some standard measures, such as glucose, ketones, and insulin, changed during fasting but that these changes were transient. He also observed deterioration in thyroid and androgen function and emphasized the muscle loss he experienced.
• Fasting can still be used for calorie management. Attia said he continues a form of time-restricted eating, generally having coffee and a low-calorie protein shake in the morning, followed by a meal around 2 p.m. and dinner around 6–7 p.m. He does this to manage total calorie intake—not because he believes the eating schedule itself has a proven special longevity effect.
• What might change his view: Attia said he would want compelling evidence from a more informative model, potentially companion dogs, before reconsidering long-term fasting as a longevity strategy.

Presenters and Sources

• Peter Attia — speaker
• Nick — interviewer
• The discussion also refers to Attia’s book, Outlive, and his past writing on fasting.