An umbrella term, not one protocol.
Intermittent fasting describes patterns that alternate eating with periods without food. Time-restricted eating limits the daily eating window; alternate-day approaches use a different schedule. These approaches should not be treated as interchangeable, and prolonged fasting is a separate practice.
Promising findings need context.
NIH describes a trial of time-restricted eating in adults with metabolic syndrome that found modest improvements over three months. NIDDK discusses research in type 2 diabetes, including weight and glucose outcomes. These findings apply to the people and protocols studied; they do not promise the same result for every person.
There is no universal day-by-day timeline.
Meal timing, food intake, medication, activity and health affect how someone responds. A claim that everyone reaches a particular physiological milestone on day 1, day 3 or week 2 would overstate what the research shows. Hunger and adaptation can also differ.
Safety comes before a schedule.
Discuss fasting with a health professional when medication or a medical condition is involved. Diabetes medicines can need adjustment to avoid low blood glucose. NIDDK identifies pregnancy as a group without adequate evidence and notes concerns about muscle loss in older adults. This article does not recommend a fasting schedule.
Keep meal planning practical.
You can plan useful meal occasions without restricting an eating window. Our Tools page helps count planned meals and explains screening estimates. It does not design a fasting protocol, diagnose a condition, or forecast weight loss.