Notes

Useful, calm content on fasting, for learning and sharing. Not medical advice. Disclaimer

Start a timer: 16:8 timer · OMAD timer · online fasting timer.

Fasting Library: structured learning path.

• Fasting Fundamentals: The main notes: what fasting is, safety, hunger, hydration, timer stages, schedules, and how to stop or eat again gently.
• How to make fasting easier: How-to notes for quieter hours: start near the overnight gap you already have, then water, an optional unsweetened mug, rest, and a window that fits a real day. Vinegar, salt stacks, and extra hours are not the method.
• Longer fasts: How-to notes for a stretch past a daily window: safety first, a plan, water, and an exit. A 72-hour challenge, stacked 16:8s, and a clinic at home are not the method.
• Very long fasts: For people who have already chosen a fast past 72 hours: signs that end it, why a clinician is the default, and a few known cases with their limits.
• Using the Clock: The timer as a tool: what a fasting clock is for, how to choose one, what this one does, and what it refuses.
• Everyday Fasting: Common questions from people actually using a window: what usually ends a fast, what to eat when you eat, first-week snags, real-life schedules, periods and hormones, why some people keep the hours, and alcohol on a daily window.
• Questions from the community: Short answers to questions people ask, with links to the notes that go into the detail. Not a salt recipe, not a plan for a week of water only, not a plan for going without water, and not a separate timer for someone already in ketosis.
• History of Fasting: From survival and ritual to medicine, protest, and modern wellness: what people did and believed, not diet prescriptions.
• Humans, Food & Feast–Famine: Meal patterns before and after agriculture, with hard limits on what prehistory can prescribe for modern schedules.
• What Research Suggests: How to read fasting studies, what TRE and related trials suggest, what headlines get wrong, how training sits with a window, what papers report as harm, and what is still unknown. Always with limits.
• Fasting, myths and science: Claims people repeat about fasting, set next to studies this library has opened. Only published notes are listed.

All notes

• Does fasting improve your eyesight?: Studies of fasting that this note opened found no change in a glasses prescription or in chart sharpness. They were Ramadan daytime fasts. The blood sugar studies involved diabetes or a forced sugar spike, not a fast in healthy people.
• Does fasting lower appetite over time?: People ask whether appetite falls after weeks of fasting, or after eating mostly protein and fat. One alternate-day trial in 16 adults found evening hunger on the fast day lower by week 2. A 6-month trial in 31 adults found no change in hunger or fullness. Both fast days still included a meal, and neither trial had a comparison group.
• Dry mouth, bad breath and a pounding heart while fasting: The NHS names dehydration as a main cause of a dry mouth, and lists fasting or crash dieting as a cause of bad breath. In one small study, breath acetone rose the longer people stayed without food. Heart palpitations are usually harmless. During a fast, stop and get checked if a pounding heartbeat keeps coming back, lasts a long time, or comes with dizziness, chest pain, fainting, or shortness of breath.
• Can I eat spicy food right after a fast?: This note found no study of spicy food straight after a fast. NHS pages say spicy food can cause or worsen heartburn and indigestion. Have a small portion first and see how it sits.
• I slipped during a fast. What now?: A few bites end the fast that was running. The hours already counted stay. You can start again after eating, or eat as you normally would. Vomiting is a reason to stop and get help if it continues.
• Do sleeping hours count toward a fast?: Sleeping hours count on this timer. A small study found lower energy use during sleep than while resting awake in bed, propped up.
• Do supplements help on a long water fast?: Do vitamins or supplements help on a long water fast? What actually runs low, what upsets an empty stomach, and why 'pure' on the label doesn't matter.
• Already in ketosis: do the timer stages still apply?: On keto and already in ketosis when you start a fast? What the timer's stage names really mean, why not to backdate the start, and how to actually check.
• Open on this clock: Open is the hour button with no finish time. The clock counts until you press End Fast. The line under the hours says there is no time cap. A full ring does not mean the fast is finished.
• History on this clock: History is the list of fasts you already finished on this clock. You can log a missed fast, correct a time, and see counts of those hours. Those counts do not keep a streak of days, and friends cannot see them.
• Dry fasting: Dry fasting means no food and no fluid. The dangers are dehydration and strain on the kidneys. This library does not give a length, a prep list, or a way to do it.
• What a long fast is not: Three days of 16:8 still include a meal each day. A 72-hour number is a time you planned to eat, not a test you have to pass. A phone cannot check your blood pressure or tell you to stop and eat.
• After the first day: Once food has been missing for about a day, hunger at the old meal time, feeling cooler, and lighter sleep are common reports. Dizziness, confusion, chest pain, and a heartbeat you cannot explain still mean stop.
• Acid reflux while fasting: Acid reflux on an empty stomach: why it happens on a fast, what baking soda really does, what people change first, and when to see a doctor.
• Which salt for a water fast?: Pink, Celtic or table salt: a teaspoon of any of them is mostly sodium. What a 2020 study of 31 pink salts found, and what matters more on a long fast.
• Presets on this clock: On this timer, 16:8, OMAD, Custom, and Open are hours you pick. A full circle does not mean your body changed. Not a ranking of 16:8 vs OMAD.
• Choosing a fasting timer: Choose a fasting timer by deciding where it has to live, how long you mean to fast, and what you want besides the hours. We make MyFastingClock, and this page includes it with the other clocks.
• What a fasting timer is for: A fasting timer counts hours. It does not clear you, sell a plan, or replace an exit. What a clock has to do, what this one does, and what it will not.
• Water and minerals past a day: Past about a day, water is still what you drink. Meals are no longer replacing sodium and the other minerals, so salt becomes a louder topic in heat and after heavy sweat. Buying a salt mix does not replace the missing meal.
• Eating again after many days: After many days without food, the first meals can still be dangerous. A clinician who can see you should plan them. We are not giving a menu, and a hospital schedule is not something to copy at home.
• Signs on a very long stretch: On a stretch past 72 hours, a quiet day is not clearance. Dizziness, confusion, chest pain, swelling, palpitations, and not being able to stand end it, including after you eat.
• If you already mean many days: For people who have already chosen a fast past 72 hours. These notes are not a challenge to go longer. Signs that end it, why a clinician is the default, and a few known cases with their limits.
• Before a longer fast: A stretch past a daily window is a different practice, not the next level after 16:8. Safety first, a plan you can say in one sentence, water, and an exit. A 72-hour challenge is not the start.
• What does not make it easier: People try vinegar, a salt packet, or a longer fast when they want the hours to feel easier. A shorter fast, water, enough food, sleep, and eating hours that fit the day are the changes that help.
• Rest days and loud weeks: A loud week is a week already full: a deadline, short sleep, illness at home, travel, or hard training. Shorten the fast, take a day of ordinary meals, or move the eating hours. Do not hold 16:8 through that week and then switch to one meal a day (OMAD) to make up for a late dinner.
• Hunger without the hacks: A mild hunger pang that rises and eases is common. Drink water, wait a few minutes, leave the kitchen, and shorten the fast if it is not mild. Vinegar, extra salt, and extra hours do not make that hour easier.
• Tea while fasting: Plain unsweetened tea is an optional cup during a fast. Milk, sugar, honey, cream, and tea lattes are food. Morning caffeine is a habit. Caffeine at night can keep you awake.
• How to start fasting: Start near the overnight gap you already have. Safety first, a first window you can live with, water, and a clock. A 72-hour challenge and a vinegar shot are not the start.
• Fasting and alcohol: Wine, beer, and a night out: alcohol is food, it belongs in the eating hours, and a drink on an empty stomach is not a fasting hack.
• Fasting, periods, and hormones: Does a daily window “wreck hormones”? Energy availability, missed periods as a stop signal, and what small time-restricted eating trials actually say, including PCOS.
• Why people keep a window: Time, money, fewer meals to plan: practical reasons people keep a daily eating window. A quieter kitchen is not a detox, and it is not a guarantee of a healthier body.
• Hunger is a signal, not a moral test: Hunger from a failed hunt and hunger on a weekday 16:8 are different jobs. Neither is a score of virtue.
• Circadian rhythm & daylight eating: Light is the main body-clock cue. Meals are a weaker one. Daylight eating is a pattern, not a recovered 16:8 and not a reason to skip dinner under a lamp.
• After agriculture: surplus and regular meals: Farms, stores, and grain made more regular meals possible. They did not invent 16:8, and they did not end famine.
• Before agriculture: hunting, gathering, sharing: How food moved in camp before farms: hunts that fail, plants and honey that hold the week, and meat that is shared wide.
• What we cannot conclude from prehistory: Fossils, ethnography, and “paleo” slogans cannot prescribe 16:8, OMAD, or a meat-only plate. What the evidence cannot do, on purpose.
• Did ancestral humans “fast”?: Irregular food access is old. A chosen 16:8 is not. What hunter-gatherer and archaeological evidence can and cannot say about skipping meals.
• From clinic to consumer app: How therapeutic fasting left the hospital and became 5:2, 16:8, stage badges, and a phone timer. A TV diet, a fitness window, and an app store listing are not a sanitarium.
• Therapeutic fasting in the 19th–20th centuries: Clinics, popular doctors, and hospital wards packaged not-eating as a treatment. Spectacle fasts, sanitariums, juice cures, and therapeutic starvation are not a 16:8 template.
• Keeping a window in real life: Restaurants, travel, shift work, and social meals: how to move a daily window without turning a late dinner into a failed streak.
• Fasting as protest & politics: Hunger strikes and campaign fasts refuse food as speech. The audience is a public or a jailer, not a diet timer.
• Open questions (what we still don’t know): What fasting trials still cannot answer: years rather than weeks, who was never enrolled, the clock versus eating less, and why a missing answer is not a plan to copy.
• Safety signals in the literature: What fasting trials actually report as harms, who they leave out, and why “the studies say it is safe” is not the same as safe for you.
• Common snags in the first weeks: Headache, gut changes, an energy crash, and a feeling that nothing is happening: what is common in the first weeks of a daily window, which feelings mean stop, and why a rough start does not mean the plan failed.
• Religious & spiritual fasts: Sacred calendars use not-eating for prayer, community, mourning, and discipline. The rules differ, and they are not a 16:8 template.
• Eating in the window: What to do with the hours when you eat: enough ordinary food, and why a quiet week on the scale is usually not a timer problem.
• Fasted weight training and fasting after a workout: Can you do fasted weight training before you eat? Can you keep a daily fasting window and still lift? What human trials say about those two questions.
• What usually ends a fast: Coffee, cream, lemon, diet soda, gum, and pills: what usually stays in the fasting hours, what counts as food, and how to pick one rule for the week.
• Fasting in ancient medicine: Physicians from the Hippocratic writings to Ayurvedic langhana sometimes reduced food for a sick person, along with gruel, rest, and other care. That sickbed plan is not a 16:8 schedule.
• Weight, body composition, and adherence: What human fasting trials actually measure on the scale, in body fat versus lean mass, and in whether people stay with the assigned hours. Not a weight-loss program.
• Fasting before it was a “biohack”: People have gone without food for lean seasons, religious calendars, illness, and protest. A numbered eating window, a ketone gadget, and the word biohack are new.
• Insulin, glucose, and meal timing: What human trials record for insulin and blood glucose when the eating hours sit earlier or later in the day. The changes are often small, and they often travel with weight loss. Not a diabetes treatment.
• Metabolic switching & fuel use: After you stop eating, the body gradually uses less stored carbohydrate and more fat, and the liver makes more ketones. Researchers call that shift metabolic switching. It is not a switch that flips at hour 16.
• Autophagy: what it is and what headlines get wrong: Autophagy is ongoing cellular recycling, not a switch that flips at hour 16 or 24. What the word means, why headlines overclaim, and what the timer label is for.
• Alternate-day & prolonged fasting studies: What human trials of alternate-day fasting, 5:2, and multi-day fasts actually test, and why those plans are not the next level after 16:8.
• Time-restricted eating (TRE) in humans: What human trials of daily eating windows suggest about weight and metabolic markers, and why time-restricted eating is not automatically better than eating less.
• How to read fasting research: A calm method for reading fasting studies and headlines: study type, who was studied, what was compared, and what a paper cannot decide for you.
• Building a sustainable fasting rhythm: How to keep a fasting practice useful over months: rest days, flexible windows, eating well when you eat, and treating the clock as a guide rather than a streak.
• When to stop a fast: How to end a fast you already started: warning signs, illness and life reasons, and planned stop times. Stopping is part of the practice, not a failed streak.
• Common fasting schedules compared (16:8, 18:6, OMAD): What 16:8, 18:6, and OMAD actually mean, how they differ from gentler 12–14 hour windows and from multi-day fasts, and why none is universally best.
• Choosing a starting window: How to pick a first fasting window: start near the overnight gap you already have (often 12–14 hours), then consider 16:8 if it still feels manageable. Why jumping to OMAD is usually a poor first step.
• What the stages on the timer mean: How the names on this timer work: approximate hour ranges, what they are not, and how to use them calmly.
• Open-ended & multi-day fasts: Why this timer has no finish time you must pay to pass, how a stretch of one to three days differs from a daily window, and why the clock can follow a plan you already have.
• Sleep, stress, and your fasting window: Why the same hours can feel easy or brutal depending on sleep, stress, training, and illness, and why a rest day is part of a sustainable practice.
• Who should be careful with fasting: A clear, incomplete safety map: who should not fast unsupervised, which conditions and medicines raise risk, and why this timer cannot decide for you.
• Breaking a fast gently: After a daily window, the first meal is usually an ordinary lunch. After a day or two without food, start smaller and wait before you eat more. We are not giving a menu.
• Hunger comes in waves: Why early hunger often peaks around usual meal times, what usually helps a mild wave, and how to tell a habit pang from a reason to stop.
• Hydration & electrolytes while fasting: During the hours without food on a daily window, drink water. A shop packet of electrolyte powder is salt and sometimes potassium or magnesium. If you take medicine or have kidney disease, ask a clinician before you use one. We are not giving a grams-per-day target.
• What is intermittent fasting?: A calm overview of intermittent fasting and time-restricted eating: what it is, common schedules, what it is not, and how to start gently.

Metabolic stages & tips · Open the fasting timer