FastWithin: Fasting Timer

FastWithin is an intermittent fasting timer and tracker built for real life, with a 3D body that shows your fasting zones hour by hour.

Most fasting apps treat a snack like a failure. FastWithin treats it like data. Ate something? Tap I ate, and your fast restarts from that exact moment. Forgot to log it? Pick "30 min ago" and the math fixes itself. Every fast and every restart stays in your history, with no judgment.

NEW: CALORIES AND A MEAL DIARY

See about how many calories you have burned right next to your zone, plus calories burned while fasting today and this week, with about how much came from fat. An estimate from your height, weight, age and sex. The meal diary lists the meals that ended your fasts, with a quick break check. Snap a photo and AI names the meal and its rough calories. A home screen widget shows your fast at a glance, and a 7-day starter gives you one small target a day for your first week.

YOUR PERSONAL FASTING COACH

Tell FastWithin your name and why you fast: health, spiritual or both. Your coach greets you by name, asks about your energy, celebrates milestones and checks in when you have been away. Log your weight weekly for a trend and a gentle pace check.

SEE YOUR FASTING ZONES BY THE HOUR

A cinematic 3D body, as a woman or a man, shows what research suggests is going on inside as you fast. Colors shift from warm amber as you digest to teal sparkles when cleanup (autophagy) may begin.

AN HONEST FASTING ZONES CHART

Fed, Settling, Switching, Fat burning, Cleanup, Deep and 48 hours plus. Each zone tells you what's happening in plain English, one practical tip, and "How we know" with real sources from NIH pages and peer-reviewed studies. We say "research suggests" and "may" on purpose, we tell you when the evidence comes from animals, and we never promise weight loss or cures.

EVERY KIND OF FAST

- 16:8, 18:6 and 20:4 daily fasting

- 24 hour fasts for one meal a day (OMAD) style eating

- Longer fasts of 36, 48 and 72 hours, with day by day guidance up to 7 days

- Breaking a fast advice that scales with how long you went

MIRROR WITHIN

See what each zone is doing on your own body, with your camera or a photo.

KITCHEN CLOSES (OPTIONAL)

Set your bedtime and FastWithin can close the kitchen 2, 3 or 4 hours before bed, with a heads up and a streak.

BUILT AROUND YOU

- One big Start fasting now button. A one minute setup.

- A Health profile with gentler goals, including for people on GLP-1 medicines

- Notifications for zone changes, your goal, water breaks and a weekly look back

- Dark and light mode, large text support, and a 2D body option

FAIR PRICING

Free for good: the timer, I ate, Kitchen closes, every zone with its sources, the 3D body, the widget and your last 7 days of meals.

Plus adds calories burned, AI photo logging (the photo is never saved by FastWithin), the coach voice, a weight chart with goal date, a spiritual pack, a weekly pattern coach, Sleep mode, an Hours bank, repeat fasts, full history and meal diary, custom goals, share cards and themes. Family Plus and Lifetime add the Family Circle: up to five people fast together and cheer each other on.

Plus is $4.99 a month or $29.99 a year with a 7-day free trial. Family Plus is $79.99 a year for up to five people. Lifetime is $249.99 once. We remind you 2 days before any trial charge, and you can cancel in Settings.

Looking for a 16:8 fasting timer, an OMAD app, an autophagy timer or a fasting tracker with calories? FastWithin does all of it.

PRIVATE BY DESIGN

No account. No sign-up. Your fasting history, name, photo, goals and weight stay on your phone. No ads and no tracking.

PLEASE NOTE

FastWithin is a timer and education app, not medical advice. Fasting is not right for everyone. Talk to a doctor first if you are pregnant or nursing, have diabetes, take medication, have a medical condition or a history of an eating disorder, and before any fast longer than 24 hours. For adults 18 and over.

Website: fastwithin.com