A diet setup calculator for Lyle McDonald's book Intermittent Modified Fasting (2026).
Live at demin.ws/imf
Given your bodyweight, body fat %, activity level, and training, it calculates everything needed to set up an IMF diet following the charts in the book:
- Diet category (1/2/3) from the sex-specific body fat table, with a DEXA correction option, plus lean body mass and fat mass
- RFL day ("fasting" day) — minimum protein target scaled to category, lean body mass and training type; estimated calories, daily deficit, and fat loss per RFL day; fish oil (EPA/DHA) dose
- Maintenance day ("feasting" day) — TDEE via the book's method (BMR by category × activity and per-hour exercise multipliers, with an optional +10% for the thermic effect of food to match the official online calculator), protein held equal to the RFL day, fat at 0.25–0.5 g/lb, carbohydrates from the remaining calories
- Weekly plan — a color-coded 7-day schedule for the chosen IMF pattern (6:1, 5:2, 4:3/3:4 alternate-day, ICR, 2:5, 1:6) with estimated weekly fat loss and total weekly deficit
Supports lb/kg, light/dark mode, and mobile widths. All values update live.
A single self-contained index.html — vanilla JavaScript, no dependencies, no
build step. Open the file in a browser and it works.
Deployed with GitHub Pages.
The calculator only covers the basic setup — read the book for the full method. Not medical advice: very-low-calorie days are not appropriate for everyone.