20:4 Warrior Diet Calculator

The Warrior Diet compresses all your eating into a four-hour evening window after a long daily fast, and that tight window is what drives the deficit. With so little time to eat, intake falls a long way — reviews put the reduction across fasting protocols at 10–30%, with the shortest windows highest (Varady et al., 2021), and this calculator estimates a 25–35% cut for a four-hour window. For the worked body — maintenance about 1,990 calories — a 30% cut is close to 600 calories a day, landing intake near 1,390. That is getting close to the 1,200-calorie floor the tool flags for women, and a lighter person or a bigger appetite cut can dip below it. As with every fasting pattern, the fasting hours do nothing magical — they simply help you eat less, and that gap is the loss. The calculator flags the floor for your own numbers.

A 600-calorie daily deficit is about 4,200 calories a week, which at roughly 7,700 calories per kilo of fat comes to about 0.54 kg — near 1.2 lb — every week for the worked body. That sits between a moderate daily window and the aggressive pace of OMAD. The speed is real, but so is the trade: a deficit this size is more likely to cost muscle and harder to hold for long, and it leaves less room above the safe intake floor. Slower loss you sustain almost always wins over months. Confirm the maintenance the estimate rests on with the TDEE Calculator, then read your weekly range above.

Fitting a Day's Food Into 4 Hours

The practical challenge of 20:4 is nutrition, not hunger. A single four-hour window is a short time to cover a full day of protein, fibre and micronutrients, and it is easy to end up eating large but nutritionally thin. If you run the Warrior schedule, make the window deliberately protein-forward and built around whole foods rather than a rushed feast. Plan the split with the Macro Calculator so the short window still covers your day.

If the four-hour window leaves you drained or unable to hit your protein, a longer eating period keeps most of the benefit with far less strain. An 18:6 or 16:8 schedule still creates a solid deficit but gives you the time and meals to eat well, which makes it easier to sustain and to protect muscle. The best schedule isn't the strictest — it's the one you can repeat. Switch the dropdown in the calculator above to compare the projected loss from a gentler window before committing to 20:4.