See what happens inside your body
Drag through a fast and watch the stages change. This is the same timeline the app shows you live, hour by hour — so you always know why you feel the way you do.
Fed state0–4 h
You're digesting your last meal. Blood sugar and insulin are up, so fat storage is on and fat burning is paused. Nothing to do but wait — this is the easy part.
Early fasting4–12 h
Insulin is falling. Your liver releases stored glycogen to keep blood sugar steady. Hunger arrives in waves timed to your usual meals — each one fades in about 20 minutes.
Fat burning12–16 h
Liver glycogen is running low, so your body ramps up fat oxidation and starts making ketones. Fat stores — including visceral fat — are now being used for fuel.
Ketosis rising16–24 h
Ketones are climbing and, for many people, appetite drops. This is the window where cellular clean-up (autophagy) is upregulated in animal studies. Sip water with a pinch of salt.
Deep fasting24–48 h
You're running mostly on fat now. Growth hormone rises, which helps protect muscle. Electrolytes (sodium, potassium, magnesium) matter more than ever — and rest is your friend.
Extended fasting48–72 h
Ketones are high and insulin is very low. Some research suggests immune cell renewal after about 72 hours. Plan a gentle refeed: small meals, protein first.
Beyond 72 hours72 h+
Only continue with medical supervision. Refeeding syndrome is a real risk after prolonged fasting — reintroduce food slowly, over a full day or more.
