Evidence-based guides on every major fasting protocol — plus a built-in timer, meal plans, and honest answers about what works and what doesn’t.
Start Here (Beginners) Find Your ProtocolSix core protocols cover almost every reason people fast — from gentle daily windows to multi-day water fasts. Pick the one that fits your goal and schedule.
Fast 16 hours, eat in an 8-hour window. The most accessible daily protocol — typically skip breakfast, eat noon to 8 PM.
16:8 & 18:6 GuideOne Meal A Day. A 23-hour fast with a single eating window. Strong appetite control and time savings, but demands careful nutrition.
Read OMAD GuideEat normally five days a week. Cap calories at ~500–600 on two non-consecutive days. Easier socially than daily fasting.
Read 5:2 GuideAlternate fasting days with normal eating days. Higher metabolic impact, less suitable for casual practice.
Read ADF GuideExtended fasting (24–72+ hours) on water only. Significant autophagy and metabolic effects — and significant risks if done wrong.
Read Water Fast GuideOne or two 24-hour fasts per week, otherwise normal eating. A flexible weekly approach popularised by Brad Pilon.
Read Eat Stop EatThe honest version: real metabolic effects, real lifestyle benefits, and a few effects the internet exaggerates. Here’s what the evidence supports.
Most fasting weight loss comes from a natural calorie deficit and improved insulin sensitivity, not magic. Weight loss guide →
Cellular cleanup ramps up after ~18–24 hours. Real, but more nuanced than headlines suggest. Autophagy science →
Stable energy without snack crashes is one of the most consistently reported subjective benefits.
Fewer meals to plan, prep, and clean up. The biggest reason people stick with fasting long-term.
Fasting windows reduce insulin exposure, which can improve markers in insulin-resistant individuals. Diabetes & fasting →
Protein intake and resistance training matter more than fasting length. Done right, you keep muscle. Muscle & fasting →
The hours you don’t eat get the attention. The hours you do eat are what determine results.
What you eat in the first 30 minutes after a long fast affects digestion, energy, and how you feel for the rest of the day.
How to Break a FastSample weekly meal plans for 16:8, OMAD, and 5:2 — with portion guidance and grocery lists.
View Meal PlansWhat breaks a fast, what doesn’t, and the truth about cream, MCT oil, and artificial sweeteners.
Coffee & FastingSodium, potassium, magnesium — why they matter most on longer fasts and how to dose them safely.
Electrolyte GuideCombining ketogenic eating with fasting accelerates ketosis but also amplifies side effects. Here’s how to combine them.
Keto + FastingMacros, nutrient density, hydration, and meal timing for sustainable results inside your eating window.
Nutrition GuidesTrack any protocol from 16h to 48h. Runs entirely in your browser — no signup, no account, your data never leaves your device.
Total Fasts
Average Duration
Longest Fast
No fasting history yet. Complete your first fast to see your statistics!
Real situations: starting from scratch, fasting around work, family meals, training days, and when something feels off.
A step-by-step first month — from your first 12-hour fast to a comfortable 16:8 routine.
Start HereHeadaches, fatigue, sleep changes, irritability — what causes them and how to handle them.
TroubleshootEnergy management, meeting culture, lunchtime workarounds, and avoiding awkward conversations.
Workplace GuideCooking for non-fasters, dinners out, holidays, and explaining your eating schedule.
Family GuideWhen to train, what to train for, and how to fuel performance inside an eating window.
Training GuideHormonal considerations, menstrual cycle timing, and protocol modifications worth knowing.
Women’s GuideWhich medications need food, which interact with fasting, and what to discuss with your doctor.
Medications GuideHow fasting windows affect sleep onset, depth, and recovery — and how to schedule meals for better rest.
Sleep GuideWho should not fast, warning signs to stop immediately, and conditions that need medical supervision.
Safety GuideThe 15 mistakes that account for most stalled progress — diagnostic format with specific fixes.
Mistakes GuideHow fasting interacts with specific conditions, hormonal contexts, and the symptoms most worth understanding properly.
Why fasting reliably lowers BP and how to handle the medication-adjustment problem.
BP GuideLevothyroxine timing, T3 effects, and the real picture vs the myths.
Thyroid GuideMicrobiome shifts, the migrating motor complex, and when fasting helps vs flares.
Gut GuideType 2 diabetes, medication adjustments, and the metabolic case for fasting.
Diabetes GuideWhat fasting actually does to cortisol, and the “adrenal fatigue” confusion.
Cortisol GuideOne of the strongest evidence bases for fasting — mechanisms, protocols, expected results.
Fatty Liver GuideTrigger or treatment? Both, depending on phase. The migraine-aware protocol.
Migraine GuideHow fasting affects mood — when it helps, when it harms, antidepressant interactions.
Mood GuideRA, psoriasis, MS, IBD — what the evidence actually shows.
Inflammation GuideFasting around chemotherapy, FMD evidence, and what the marketing oversells.
Cancer GuideCautious approach for an emerging field — when fasting may help, when it triggers crashes.
Long COVID GuideFasting in specific life stages and contexts where the standard advice doesn’t quite fit.
What changes hormonally and which protocols suit which symptom patterns.
Menopause GuideWhen fasting helps fertility, when it harms — and timing around conception attempts.
Fertility GuideWhy fasting is generally not recommended for teens — for parents searching about it.
Teen GuideSpecific guides for the major training contexts — what fasted training actually does and which sessions to fuel.
Build muscle while losing fat simultaneously — when it’s realistic and how to actually do it.
Recomp GuideReal benefits, real limits — and the truth about “burning more fat fasted.”
Fasted CardioMarathon, triathlon, ultra — fueling strategy and metabolic flexibility.
Endurance GuideWhere fasting fits in prep timeline, peak week, and post-show recovery.
Contest PrepWhat works fasted, what breaks the fast, and a sensible DIY stack.
Pre-WorkoutDetailed guides for specific fasting structures and the approaches you’ll encounter online.
Direct head-to-head comparison and decision guide for the main daily protocols.
Compare ProtocolsOri Hofmekler’s protocol — between OMAD and 18:6 with a specific structure.
Warrior DietEat Stop Eat with day-to-day flexibility — for variable schedules.
Rolling 24sThe intermediate-length protocol — deeper than daily, shorter than multi-day.
36-Hour FastValter Longo’s 5-day protocol — DIY version, effects, when to use.
FMD GuideHonest head-to-head with the other approaches you’ll encounter — and how to combine them when it makes sense.
What head-to-head trials show and which approach suits which person.
vs CountingTwo paths to similar metabolic destinations — and the case for combining them.
vs KetoThe strongest long-term evidence base + the strongest metabolic intervention.
vs MediterraneanHonest comparison with Ozempic, Wegovy, Mounjaro — and how to combine.
vs GLP-1Knowing whether fasting is working, what to measure, and what to ignore.
What to measure, what to ignore, and the honest assessment timeline.
Diagnostic GuideHonest answers about what breaks a fast, what doesn’t, and what’s worth using.
Which sweeteners break a fast, which don’t — and the cephalic phase question.
Sweeteners GuideWhat breaks a fast, what doesn’t — including butter coffee, MCT oil, milk.
Coffee GuideFasting has to fit your life — alcohol, travel, age, budget, diet style. Practical guides for the situations that actually come up.
Tolerance drops, sleep degrades faster, calories add up — how to drink with the fewest downsides.
Alcohol GuideUse a defined fast to reset circadian rhythm across time zones — the practical protocol.
Travel GuideCheap, nutrient-dense eating, sample grocery list, and what to skip from the wellness aisle.
Budget GuideHitting protein targets on plants in a compressed eating window — strategy and food list.
Vegan GuideTen specific recipes for the first meal after a fast — short, long, and extended.
Refeed RecipesAutophagy, ketosis, gluconeogenesis, refeeding — every term used on this site, defined plainly.
GlossarySummaries of major fasting studies — what they actually measured and what we can conclude.
ResearchHonest reviews of the popular fasting apps and what to look for in a tracker.
Apps GuideHunger waves, decision fatigue, and the mental side of changing how you eat.
PsychologyWhich metrics actually matter, which to ignore, and how to know if it’s working.
TrackingPick a protocol, set the timer, and learn as you go. Everything on this site is free.
Beginner Guide Open TimerFreeFasting is educational. It is not medical advice. Consult a qualified healthcare professional before starting any fasting protocol, especially if you take medication, are pregnant, or have a medical condition.