Fasting Clock

Start your fast and watch metabolic phases unfold — from fat burning at 12h to autophagy at 17h, gut reset at 24h, and extended resets up to 72h. Personalized for keto, insulin resistance, and cycle-aware fasting.

How to use this

  1. Choose water-only or assisted fasting, pick your goal hours, and set your profile for personalized guidance.
  2. Tap Start fast when you finish your last bite. When you reach your goal, we show how to break the fast with meal ideas.
  3. Follow doctor-sourced tips for electrolytes, cycle timing, and when to break your fast safely.
Fasting type
Goal duration

Optional: Dr. Boz Ratio (glucose ÷ ketones)

Track metabolic progress during your fast. Target under 80 for ketosis; under 40 for deeper benefits (Dr. Boz).

Breaking intermittent fast (≤18h)

Shorter fasts (16:8, 18:6) are the easiest to break. Dr. Mindy still recommends protein, healthy fat, and fiber — your first meal sets blood sugar for the eating window.

How to break your fast

  1. 1Open your eating window with a balanced low-carb meal — not snacks or grazing.
  2. 2Prioritize protein (eggs, chicken, fish, cottage cheese) plus healthy fat.
  3. 3Add non-starchy vegetables or a small side of greens for fiber.
  4. 4Dr. Westman: eat when hungry, stop when full — your first meal after IF is not an excuse to overeat.
  5. 5Stay low carb to maintain the metabolic benefits you built during the fast.

What to avoid

  • • Breaking with toast, oatmeal, or cereal — spikes insulin and ends fat-burning quickly.
  • • Sweetened coffee drinks or "keto" bars loaded with sugar alcohols as your first bite.
  • • Skipping protein and eating only nuts or cheese — balance matters.

Expert tips

  • Dr. Mindy Pelz: 13–16 hour fasts are her baseline — break them with real food: protein, fat, and fiber at every meal.
  • Dr. Eric Westman: On keto, hunger stays low — your first meal can be lunch-sized. No need to "make up" missed calories.
  • Dr. Boz: If you track the Dr. Boz Ratio, your first meal should nudge you toward fat burning, not a glucose spike above 80.

Suggested break-fast meals

All recipes

Read the full break-fast guide →

Not medical advice. Guidance synthesizes public teachings from Dr. Mindy Pelz, Dr. Eric Westman, and Dr. Boz. Talk to your doctor before fasting — especially on diabetes, blood pressure, or kidney medications.

Fasting timer

Ready to start

00:00:00

Set your goal and tap Start fast. Your timer persists if you close the tab.

Frequently asked questions

What is assisted fasting vs water-only?

Water-only means plain water — strictest, best for shorter fasts. Assisted adds electrolytes, bouillon/broth for sodium (Dr. Westman), and black coffee or tea without calories (Dr. Boz). Both avoid food and caloric drinks.

When does autophagy start?

Dr. Mindy Pelz cites research showing autophagy increases around 17 hours without food. A 24-hour fast is her recommended "gut reset" for weekly use.

Is extended fasting safe?

Dr. Westman cautions that fasts beyond 24 hours carry electrolyte and refeeding risks — especially on diabetes or blood pressure medications. Dr. Boz adds that severe insulin resistance may require stabilizing with low-carb eating before longer fasts. Always consult your doctor.

Metabolic Low Carb Calculator · https://metaboliclowcarb.com