Free tool · Perimenopause-aware

Intermittent Fasting Calculator

Pick a protocol, set when you want to start eating, and see your full daily schedule. Includes a peri-friendly warning for fasts that may backfire.

Format: fasting hours : eating hours

10:00 AM

Most peri-friendly: 8–10 AM (aligns with cortisol curve).

Your eating window

10:00 AM8:00 PM

10 hours of eating

Fasting window8:00 PM – 10:00 AM
Fasting length14 hours

Hitting 100+ g protein/day in your eating window matters more than the window length.

Intermittent fasting after 40: nuance required

IF works for many women in perimenopause — but the protocols that exploded online were studied mostly in men or younger women. Translating them straight across is where things break.

What works

  • 12:12 or 14:10 — gentle, sustainable, improves insulin sensitivity.
  • Eating earlier in the day (front-loading calories).
  • Stopping eating 2–3 hours before bed.

What backfires

  • Fasts of 18+ hours when sleep is already disrupted.
  • Skipping breakfast then under-eating all day → muscle loss.
  • IF + heavy strength training without enough protein.

Signs to back off

Shorter cycles, worse hot flashes, anxiety creep, mid-afternoon energy crashes, hair shedding. Any of these = shorten the fast.

Window length is one variable. Lila handles the rest.

Personalized eating windows that flex with your cycle and symptoms.