Question 129 of 433
What about multi-day water fasts?
The short answer
A fast of two or three days produces real metabolic changes, and some people feel better for it. It has not been shown to extend life, and it is not safe for everyone.
After about a day without food the body shifts to burning fat and making ketones, insulin falls, and cells increase their recycling activity. Enthusiasts, and I have been among them, describe an occasional 72-hour fast as a reset. A large observational study from a European fasting clinic reported weight loss, lower blood pressure, and few complications under medical supervision.
The cautions are serious. Some of the weight lost is muscle. Blood pressure and blood sugar medications must be adjusted. Fasting can trigger gout, gallstones, dangerous rhythm changes, and, on refeeding, shifts in blood salts. Do not attempt it if you are over 70, underweight, pregnant, have diabetes treated with medication, heart rhythm problems, or a history of disordered eating. For many adults, avoiding habitual late-night eating is a simpler option. Even an overnight fasting window should fit medications, nutrition needs, and eating-disorder history.
“This book is for education. It is not medical advice, and reading it does not make you my patient or create a doctor-patient relationship.” From the book’s medical disclaimer. Full disclaimer
LIMITED HUMAN DATA — Supervised multi-day fasting: metabolic changes and risks; longevity benefit is unproven.Evidence grade (draft mapping)BLimited or small human studiesPart 9, Q129 · Part sources
From Longevity Unmasked by Afshine Ash Emrani, MD, FACC. Medical disclaimer. This book is for education. It is not medical advice, and reading it does not make you my patient or create a doctor-patient relationship. Nothing here is meant to diagnose, treat, cure, or prevent any disease. Medicine is personal: a test, drug, supplement, or exercise plan that helps one person can harm another. Do not start, stop, or change any medication or treatment because of something you read in these pages. Talk with a licensed clinician who knows your history first. If you think you are having a medical emergency, call 911. The author disclaims responsibility for any loss or harm arising from use of the information in this book.