Extended fasting is powerful, but it’s not harmless. This article covers the most important fasting risks and downsides, backed by physiology, data, and real experience, to help you avoid common mistakes.

Real data on fasting weight loss vs fasting fat loss. See why early weight drops fast, how much fat you actually lose, and what happens after refeeding.

Extended fasting temporarily lowers testosterone, but research and real data show it rebounds during refeeding. Here’s how my levels changed across two multi-day water fasts and why fasting may actually support healthier long-term hormone balance.

Extended fasting can dramatically improve blood sugar regulation and insulin sensitivity. Here’s my real Dexcom CGM data and fasting results.

Extended fasting doesn’t just change your weight - it transforms your biomarkers. Over 10 months, my 9- and 10-day water fasts improved 8 out of 10 InsideTracker biomarker categories, especially Heart Health, Metabolism, and Inflammation. See how fasting biomarkers like ApoB, glucose, triglycerides, and hsCRP shifted before, during, and after fasting - and why proper refeeding makes all the difference.

How fast do ketones rise during fasting? In my 7-, 9-, and 10-day water fasts, I tracked how quickly I entered ketosis and what made the biggest difference. Turns out, movement early in the fast helps you reach deep ketosis faster — and burn more fat along the way. Here’s how glucose drops, ketones rise, and why fasting ketosis is totally different from dangerous ketoacidosis.

Learn how intermittent fasting works — from glucose and insulin regulation to fat burning and autophagy. Discover 44 scientifically supported fasting benefits backed by research papers and ranked by strength of evidence.

Fasting activates autophagy — your body’s cellular recycling system. Learn how different fasting lengths boost repair, longevity, and overall health.

Intermittent fasting for weight loss isn’t a trend — it’s a proven way to train your body to burn fat efficiently, stabilize energy, and improve long-term health. Learn how it works, how to start, and what science really says about the fastest and safest path to sustainable fat loss.

Most think fasting is about weight loss. The truth? Extended fasting resets your body on every level - metabolism, hormones, and cellular health.

I recently completed a 10-day water fast and documented each day - from deep sleep and muscle cramps to glucose and ketone highs, mental clarity, and a smooth refeed. In this fasting diary, I share daily notes, challenges, weight loss results, and lessons learned about electrolytes, workouts, and mindset. If you’re curious about extended fasting for health benefits beyond weight loss, here’s exactly what happened to my body and mind.

From my first 24-hour fast to a 9-day water fast — here’s how fasting reshaped my mindset, health, and confidence over 25 years.

Discover my personal 16:8 intermittent fasting routine — from early-morning workouts to strategic meal timing — and learn practical tips for handling hunger, staying flexible, and making IF a sustainable lifestyle.

Breaking an extended fast the right way is just as important as the fast itself. Learn what to eat, what to avoid, and how to reintroduce food safely — with a simple, science-backed refeeding guide.

Extended fasting is tough — but it doesn’t have to be torture. These 20 tips will make your next multi-day fast easier, safer, and more effective.

I completed a full 7-day water fast and tracked everything: weight, fat, lean mass, glucose, ketones, HRV, sleep, and refeeding. If you’ve ever wondered what real 7-day fast results look like, here’s the detailed, data-backed breakdown.