Extended fasting works—learn the refeeding rules before you try it

Extended fasts accelerate benefits by keeping insulin low for longer, but the way you end them matters. During a 48–72 hour fast, your body shifts to ketones and conserves minerals carefully. When you refeed, insulin rises, cells begin rebuilding glycogen and protein, and they need electrolytes to do it. If you flood the system too fast after a long absence of food, you can feel puffy, crampy, or just plain off.

This is why the first meal should be small and simple. A few bites of protein and vegetables, a pause, then a regular meal. Many also use bone broth during the fast to provide sodium and a touch of amino acids, which makes the transition smoother. It’s not “pure” water-only fasting, but it’s far more comfortable for most and honors the spirit of healing.

A micro-anecdote: someone tried to break a 72-hour fast with pizza and soda and felt awful for 24 hours, with bloating and fatigue. The next time, they used eggs and spinach, waited an hour, and then had salmon and vegetables. No issues, and they noted better energy that afternoon.

There is also a rare but real condition called refeeding syndrome after prolonged malnutrition, not usually after brief therapeutic fasts in otherwise nourished adults. Still, the principle applies: reintroduce food gently and support electrolytes. Keep training easy on refeed day and let your system equilibrate.

Mechanistically, refeeding increases insulin, which drives phosphate, potassium, and magnesium into cells for glycogen and protein synthesis. Rapid shifts can cause symptoms if stores are low. A staged refeed with adequate electrolytes prevents this, while extended fasting itself promotes fat loss, improved insulin sensitivity, and autophagy.

Before attempting 48–72 hours, build up with two weeks of 16:8 and one or two 24–36 hour fasts so your body knows the drill. During the longer fast, sip water and mineral water, and consider a salty broth to avoid headaches and cramps. When you break, start with a small protein-and-veg dish and give yourself 30–60 minutes before a normal meal, keeping your training easy that day. Notice how you feel and keep notes so your next extended fast is even smoother. Put the plan on your calendar for a quiet week and try it with intention.