life1life1Intermittent fasting usually means time-restricted eating: all meals inside a fixed window, nothing but water, coffee or tea outside it. The window is the whole method; there are no special foods.
16:8 is the best known: a 16-hour fast and an 8-hour eating window, for example noon to 8 pm. 14:10 is gentler and easier to keep on social days. 18:6 and 20:4 are stricter and harder to sustain. Alternate-day and 5:2 patterns restrict calories on some days rather than hours.
A 12-month randomised trial published in the New England Journal of Medicine in 2022 compared time-restricted eating plus calorie restriction with calorie restriction alone in adults with obesity and found no significant difference in weight loss between the groups. Shorter trials point the same way: the window helps some people eat less, and the eating less is what moves weight. Fasting is a tool for adherence, not a separate mechanism.
People who are pregnant or breastfeeding, anyone with a history of disordered eating, people taking medication timed to meals such as insulin, and anyone under 18. If any of that applies, ask a clinician before changing the window.
The two things that undo a fasting record are a late dinner you forgot to log and a start time you had to guess. A timer with an editable start fixes both.
In LIFE1. LIFE1’s fasting timer has an editable start, shows the ring on Apple Watch and Wear OS, and sits in the same app as the meal scanner and the Health Score. Each protocol sets a default window that you can change.
Black coffee, tea and water are usually counted as inside the fast. Anything with calories, including milk and sugar, is usually counted as breaking it.
Trials have not shown a clear advantage for a longer fast once calories are matched. The better window is the one you keep.
Many people do easy sessions fasted. Hard sessions often go better with food on board. Watch how you feel and how the session goes, and adjust.
LIFE1 shows what you measured and what published guidelines say. It does not diagnose, interpret or treat. This page is general information, not medical advice.