Time-Restricted Eating
Time-Restricted Eating — Time-restricted eating (TRE) is a form of intermittent fasting in which all daily food intake is confined to a fixed window of typically 6 to 12 hours, with the remaining hours spent fasting. The most popular protocol is 16:8 (16-hour fast, 8-hour eating window). TRE is studied for both weight management and circadian metabolic effects.
What is time-restricted eating?
Time-restricted eating (TRE) is a sub-category of intermittent fasting in which the eating period is confined to a fixed daily window. Common windows include:
- 12:12 — beginner; eat between 7am-7pm, fast 7pm-7am
- 14:10 — moderate; 10-hour eating window
- 16:8 — most popular; 8-hour eating window (e.g., noon-8pm)
- 18:6 — advanced
- 20:4 — “Warrior Diet”; very narrow window
Unlike alternate-day fasting or 5:2 protocols, TRE does not prescribe a calorie reduction on fasting hours; it simply confines whatever the person eats to a window. Total daily calories are determined by what is consumed in the window.
How does TRE work?
Two mechanisms are proposed:
- Circadian alignment — eating during daylight hours is metabolically distinct from eating at night, with better postprandial glucose handling and improved sleep (Sutton et al., 2018, Cell Metabolism)
- Spontaneous calorie reduction — many people find it harder to over-eat in 8 hours than 16 hours, producing an unintended deficit
Recent trials are mixed. Liu et al., 2022 in NEJM found 16:8 TRE produced weight loss equivalent to (not better than) standard calorie restriction over 12 months when calories were matched. Earlier short-duration trials had suggested unique TRE benefits that have not consistently replicated.
Why TRE matters in app-based tracking
TRE pairs well with calorie tracking apps because it reduces decision fatigue (no eating outside the window) without imposing food restrictions. For users:
- Apps that timestamp every entry can visualize compliance with the window
- TRE does not suspend energy balance — overeating during the window still produces weight gain
- Coffee, tea, and water are typically permitted during fasting hours; flavored or calorie-containing beverages break the fast
Like other forms of intermittent fasting, TRE is not appropriate for those with disordered eating histories, in pregnancy, or in growing adolescents. See intermittent fasting, carb cycling, and refeed days.