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.