The Fasting Cheatsheet (In Progress)

This page is reference material. It assumes you’ve read Fasting Basics and Fasting Game Plan, or that you’re coming here for specific protocol detail rather than conceptual setup. The format is intentionally dense — direct instruction rather than explanation. The high-level “why and when” lives in the Game Plan. This page is “exactly how.”

The Protocol Spectrum

Different fasting durations access different physiological effects.

• 12-14 hours (overnight TRE): Basic insulin reset, MMC cycling, mild overnight ketosis. Most people achieve this without thinking about it. The biological default.
• 16-18 hours: Deeper insulin suppression, glycogen depletion begins, light autophagy upregulation, and ketone production starts.
• 20-24 hours: Glycogen substantially depleted, ketogenesis active, growth hormone elevation, substantial autophagy upregulation.
• 24-48 hours: Deeper ketosis, peak growth hormone pulse amplitudes, substantial inflammation reduction, peak fat mobilisation per unit time.
• 48-72 hours: Stem cell activation begins, immune cell turnover initiates, and deeper autophagy across more tissues.
• 3-5 days: Peak therapeutic effects. Longo’s stem cell regeneration window, immune system reset, substantial IGF-1 suppression, peak ketosis (typically 3-5 mmol/L BHB).
• 5-7 days: Sustained therapeutic effects. Diminishing marginal benefit per additional day. Increasing risk profile.
• 7+ days: Generally requires medical supervision. Refeeding syndrome risk increases. Most well-characterised therapeutic effects are accessible within 3-5 days.

Match duration to the goal. Daily TRE for general health. Periodic longer fasts for deeper adaptations. Avoid the temptation to go longer than necessary.

Daily Time-Restricted Eating Protocols

• 12:12: 12-hour eating window, 12-hour fast. Finish dinner by 7-8 PM, breakfast at 7-8 AM. The biological baseline. Most metabolically healthy adults do this naturally. Good starting point for people who currently snack constantly.
• 14:10: 14-hour fast, 10-hour eating window. Finish dinner by 7 PM, breakfast at 9 AM. Moderate progression. Most women find this more sustainable long-term than aggressive 16:8.
• 16:8 Leangains: 16-hour fast, 8-hour eating window. Popularised by Martin Berkhan. Typical implementation: finish dinner by 7 PM, first meal at 11 AM, second meal around 3 PM, third meal by 7 PM. The most common protocol in the popular literature.
• 18:6: 18-hour fast, 6-hour eating window. Typical implementation: 1 PM to 7 PM eating window. Substantial overlap between Leangains and OMAD approaches. Useful for fat loss and metabolic flexibility.
• 20:4 Warrior Diet: 20-hour fast, 4-hour eating window. Created by Ori Hofmekler, inspired by ancient warrior cultures that ate primarily in the evening. Typical implementation: one large evening meal, possibly preceded by light eating in the late afternoon. Stronger autophagy and ketosis effects than 16:8.
• OMAD (One Meal A Day): 22-23 hour fast, single eating window of 1-2 hours. The simplest fasting protocol to implement (no decisions about when to eat), but requires a substantial meal that some people find difficult to consume in a single sitting. Useful for fat loss because compliance is easy; may not suit muscle building because of a single anabolic stimulus per day.

Practical considerations for daily TRE:

• Pick a window that suits your social and family life. The protocol that fits your life is the one you’ll do.
• Keep windows consistent. Shifting eating times daily disrupts the circadian rhythm.
• Generally, place the window earlier in the day rather than later. Early TRE (eating window ending mid-afternoon) produces better metabolic markers than late TRE in most research.
• Don’t eat within 2-3 hours of bed, regardless of which window you choose.
• Hydrate substantially during the fasting window.

24-Hour and 36-Hour Fasts

• 24-hour fast (Eat Stop Eat): Popularised by Brad Pilon. Eat dinner one evening, fast until dinner the next evening. Simple implementation, no full-day food avoidance, fits around social meals.
  • Frequency: once or twice per week for general health, less frequently for highly active people, more frequently for therapeutic applications.
• 36-hour fast: Eat dinner one evening, skip all meals the next day, eat dinner the following day. One full day plus the surrounding overnight fasts. More substantial ketosis and growth hormone effects than 24-hour fasts.
  • Frequency: once per week to once per month, depending on goals.

What to expect during 24-36 hour fasts:

• Hunger waves at expected meal times, typically resolving within 20-30 minutes
• Initial irritability or low energy for first-time fasters
• Improved mental clarity from hour 16-20 onwards as ketones rise
• Mild cold sensitivity
• Adequate electrolyte intake essential to avoid headaches and lightheadedness

48-Hour Fasts

48 hours produces substantial deeper ketosis (typically 1.5-3 mmol/L BHB by hour 48), measurable autophagy upregulation, and clear hormonal shifts. The transition through the “keto flu” zone is typically completed by hour 36-48.

Frequency: monthly to quarterly for general health applications.

Practical implementation:

• Last meal Saturday evening
• All Sunday: water, coffee, tea, electrolytes only
• All Monday: water, coffee, tea, electrolytes only
• Break fast Monday evening

Most people find 48-hour fasts substantially easier than the 24-36 hour window because the body has more fully transitioned into the fasted state by hour 30-40. The hunger of the second day is typically lower than the hunger of the first.

Extended Water Fasts (3-5+ days)

These access the stronger therapeutic effects: stem cell regeneration, substantial immune cell turnover, peak autophagy, and substantial IGF-1 suppression.

Frequency: quarterly for general therapeutic purposes (Longo recommendation), once or twice yearly for general health maintenance.

Day-by-day protocol (synthesised from Sim Land’s practitioner protocols, adjusted for primary research where applicable):

Day 1 (and the evening before):

Pre-fast meal: low-carbohydrate, moderate protein, adequate fat. Helps deplete glycogen faster and primes the metabolic transition. Final eating window 6 PM the day before starting.

Morning of Day 1:

• Drink water with a pinch of sea salt on waking
• Begin electrolyte protocol (covered below)
• Morning routine: meditation, light movement, sunlight exposure
• Don’t drink excessive water (more on this below)

Throughout Day 1:

• Black coffee, tea, sparkling water acceptable
• Electrolyte solution (recipe below) once or twice
• Light activity acceptable; avoid intense exercise

Expected experience: hunger waves, possible headache, and possible low energy. Mostly tolerable for people with reasonable metabolic flexibility.

Day 2:

The transition day. Many people find this the hardest day because the body has depleted glycogen but hasn’t yet ramped up ketone production sufficiently to feel adapted.

• Continue electrolyte protocol
• Coffee/tea/water as needed
• Light to moderate activity acceptable
• Walking is particularly useful. Many people report substantial hunger reduction during walks

Expected experience: Ketosis becoming established (blood BHB typically 0.5-1.5 mmol/L by the end of day 2). Energy may feel limited. Mental clarity often begins to emerge in the evening.

Day 3:

Most people report substantial improvement starting day 3. Ketosis is well-established (typical BHB 1.5-3.0 mmol/L). Hunger has dropped substantially or disappeared entirely. Mental clarity is often striking.

• Continue electrolyte protocol
• Activity level can increase modestly
• Walking, light yoga, and gentle movement are particularly good

Expected experience: the “fasted state” the protocols promise. Many people describe a characteristic feeling of cleanness and clarity.

Days 4-5:

Sustained adapted fasting. Ketones may continue rising (typical BHB 2-5 mmol/L). Energy is typically stable. Hunger is largely absent.

• Continue electrolyte protocol
• Monitor for signs of overdoing it (covered below)
• Plan break-fast meals for Day 5 or 6

Breaking the fast:

This is the most important practical detail for longer fasts. Breaking incorrectly produces more discomfort than the fast itself and can be medically dangerous after 5+ day fasts (refeeding syndrome).

After a 3-5 day fast, break with:

Hour 0 (the moment you break):

• Bone broth (small cup, 6-8 oz)
• Or hot water with a tablespoon of apple cider vinegar and a squeeze of lemon
• Or a small amount of fermented food (a few spoonfuls of sauerkraut)
• Wait 30-60 minutes

Hour 1:

• Small serving of easily digestible protein
• 2-3 eggs, or a small piece of fatty fish
• A small portion of cooked vegetables
• Avoid raw vegetables, heavy red meat, and high-carbohydrate foods at this stage

Hour 2-3:

• Slightly more substantial meal if appetite has returned
• Continue with easily digestible proteins, cooked vegetables, and healthy fats
• Avoid grains, sugars, and processed foods for the first 24 hours of refeeding

Days 2-3 of refeeding:

• Gradual return to normal eating
• Slight caloric surplus over maintenance to support refeeding
• Continue prioritising whole foods, adequate protein, vegetables, and healthy fats

Critical – Refeeding Syndrome: After fasts of 5+ days (or in malnourished individuals after shorter fasts), the metabolic shift back to fed-state can produce dangerous electrolyte shifts as insulin signalling resumes and the body suddenly mobilises phosphate, potassium, and magnesium into cells. Severe refeeding syndrome can be fatal. Symptoms include muscle weakness, confusion, cardiac arrhythmia, and seizures. The risk is highest after extended fasts in already-depleted individuals.

Mitigation:

• Break extended fasts gradually as described above, not with a large meal
• Maintain electrolyte intake throughout the fast and during refeeding
• For fasts beyond 5-7 days, work with a physician familiar with extended fasting
• If you experience any concerning symptoms during refeeding, seek medical attention

The Fasting Mimicking Diet (FMD)

Developed by Valter Longo at USC. A 5-day low-calorie protocol that produces many of the metabolic effects of water-only fasting while allowing some food intake. More tolerable than water fasting and safer for people who can’t safely do extended water fasts.

Protocol overview:

Day 1: ~1,090 kcal

• 10% protein, 55% fat, 35% carbohydrates
• From plant-based sources (nuts, vegetables, soups, and small amounts of olive oil)

Days 2-5: ~725 kcal per day

• 10% protein, 45% fat, 45% carbohydrates
• Same plant-based emphasis

Day 6: transition meal

• Light return to eating
• Complex carbohydrates, vegetables, and minimal animal foods

Day 7+: return to normal eating

The commercial product: Longo’s L-Nutra company sells ProLon, a packaged 5-day FMD kit. The underlying science is sound; the commercial dimension warrants noting. Anyone wanting to follow the FMD protocol can construct it from whole foods following the macronutrient ratios above; the commercial product is convenient.

Clinical evidence: Wei et al. 2017 Science Translational Medicine and subsequent trials have shown FMD produces reductions in CRP, IGF-1, blood glucose, blood pressure, and cardiovascular risk markers, with effects persisting weeks to months after the protocol concludes. One cycle quarterly approximates the practitioner recommendation.

Targeted Intermittent Fasting (for Training)

For people who want to combine fasting with resistance training without compromising training adaptation. Originally articulated by Land in Metabolic Autophagy; the underlying mechanism (protein during workout to mitigate catabolism while maintaining most of the fasted state benefit) is supported by training-fasted research.

The protocol:

• Fast for 18-20 hours before training
• Consume only water, zero-calorie tea, or coffee during the fasted period
• 30-60 minutes before training, consume 20-30g of high-quality protein (whey protein isolate is standard; rice protein is a reasonable alternative)
• Continue training with protein in the system
• Post-workout: wait 60-120 minutes before the main meal
• Eat remaining daily calories in 2-3 hour eating window post-workout

Optional additions during pre-workout protein:

• 3-5g creatine (no insulin spike)
• 2-5g beta-alanine (carnosine precursor for high-rep work)
• 80-160mg caffeine if not already caffeinated

What to avoid in pre-workout protein:

• Artificial sweeteners (sucralose, aspartame, acesulfame-K)
• High-carbohydrate additives
• BCAA powders with added flavourings and sweeteners

The rationale:

• The protein provides amino acids during the workout to support muscle protein synthesis without breaking the substantial fasted-state benefits
• Resistance training itself triggers MPS regardless of feeding state
• Post-workout meal completes the anabolic response
• Total daily calories distributed in 2-3 hour window means most calories arrive during the highest insulin sensitivity of the day
• Maintains most of fasting’s metabolic benefits while preserving training adaptation

Use TIF when:

• Training resistance training 3-5 times per week
• Goal is body composition (fat loss while maintaining or building muscle)
• Comfortable with 18-20 hour daily fasting windows
• Already keto-adapted or metabolically flexible

Don’t use TIF when:

• New to fasting (build up to 16:8 first)
• New to resistance training (focus on training consistency first)
• Already at low body fat with primary muscle-building goal (more frequent feeding may serve you better)
• Substantial life stress or sleep disruption

Feast-Famine Cycling

5-1-1 weekly approximation:

• 5 days: lower-carbohydrate, possibly ketogenic eating, modest portions
• 1 day: 24-hour fast
• 1 day: feast day with abundant whole foods, including some carbohydrates

4-2-1:

• 4 days: ketogenic or low-carb
• 2 days: 24-hour fasts
• 1 day: feast

2-2-3:

• 2 days: ketogenic
• 2 days: 24-hour fasts
• 3 days: moderate eating with carbohydrate

Vary across seasons as covered in the Game Plan.

Alternate-Day Fasting and 5:2

These protocols allow some caloric intake on “fasting” days. Worth understanding, but generally less effective than complete fasting on the same schedule:

Alternate-Day Fasting: Fast every other day, eat normally on non-fast days. Modified ADF allows 500 kcal on fast days. Krista Varady’s research at UIC has shown ADF produces weight loss and metabolic improvements comparable to continuous caloric restriction.

5:2 Diet: Eat normally 5 days per week, restrict to 500 kcal (women) or 600 kcal (men) on 2 non-consecutive days. Popularised by Michael Mosley.

Honestly?

• They produce some of the benefits of fasting, but generally less than the equivalent of complete fasting
• The 500-600 kcal still kicks the body out of a full fasted state
• Compliance is often the limiting factor. These protocols may be easier to maintain than complete fasting for some people
• The clinical evidence is comparable to standard caloric restriction; they’re not clearly superior to just eating less
• The metabolic benefits of fasting depend substantially on cumulative time in the fasted state, which these protocols compromise

If complete fasting works for you, it produces stronger effects per day of intervention. If complete fasting is too difficult, modified ADF or 5:2 are reasonable alternatives that produce many of the benefits.

Dry Fasting

Dry fasting involves no fluid intake during the fasting period. Practised in some religious traditions (Yom Kippur is approximately 25 hours of complete dry fasting; certain Islamic practices include dry components) and promoted by some practitioners as accelerating the effects of standard water fasting.

The popular claim: “One day of dry fasting equals three days of water fasting.”

The reality: This claim has essentially no primary research support. It traces to practitioner extrapolation and has been repeated extensively in the popular fasting literature, but the underlying biology hasn’t been studied in a way that would validate the specific 3x ratio. The mechanism that’s proposed (the body generating metabolic water from triglyceride oxidation, accelerating the metabolic shift) is legit, but the magnitude of the effect is speculative.

What we do know:

• Limited dry fasting (12-24 hours, Ramadan-style) is well-tolerated by most healthy adults
• Extended dry fasting (beyond 24-36 hours) carries substantial dehydration risk
• The Ramadan literature provides the largest natural experiment in periodic dry fasting; outcomes vary, but adverse events are rare in healthy adults observing properly
• Dry fasting in hot climates or with substantial physical activity is more dangerous

Practical guidance if you choose to dry fast:

Soft dry fast vs hard dry fast:

• Soft dry fast: no oral intake, but allows contact with water on skin (showering, washing)
• Hard dry fast: no oral intake and no skin contact with water

Soft dry fasting is what most religious traditions practice and what the limited research has examined.

Maximum duration recommendations:

• 12-16 hours: well-tolerated by most healthy adults
• 16-24 hours: generally safe for healthy adults with proper preparation
• 24+ hours: significant dehydration risk; not recommended without medical supervision
• Don’t combine dry fasting with substantial exercise, hot weather, or sauna

Preparation:

• Drink substantial water and consume vegetables the day before
• Avoid alcohol, caffeine, and salty foods in the 24 hours before
• Don’t begin dry fasting if already dehydrated

Signs to break the fast:

• Persistent dizziness or lightheadedness
• Severe dry mouth or cracked lips
• Dark or absent urine
• Confusion or altered mental status
• Heart palpitations

Dry fasting has its place in religious and cultural traditions and is reasonably safe in limited durations for healthy adults, but the specific “3x amplification” claims widely circulated in the practitioner literature aren’t well-supported. People interested in deeper fasting effects are generally better served by extended water fasting than by attempting dry fasting protocols.

What You Can Drink While Fasting

The general principle: zero-calorie liquids that don’t trigger insulin or break ketosis.

Always fine:

• Plain water (still or sparkling): The default. Don’t drink excessive amounts (covered in electrolyte section below).
• Black coffee: Two to four cups per day is acceptable. Higher amounts may interfere with sleep and substantially elevate cortisol. Personally, I’m sceptical about excessive consumption of coffee. 
• Plain tea: Black, green, white, oolong, herbal. All fine in unlimited reasonable amounts.
• Mineral water: Provides some natural electrolytes alongside hydration.

Generally fine with caveats:

• Lemon water with a slice or squeeze of lemon: Trace calories from the lemon won’t break a meaningful fast. Larger quantities of lemon juice approach caloric territory.
• Apple cider vinegar (1-2 tablespoons in water): Trace calories, may support insulin sensitivity, may reduce hunger.
• Salt water: A pinch of sea salt in water supports electrolyte balance during fasting.
• Bone broth: Technically contains calories but typically allowed in practitioner protocols because of electrolyte content and the way amino acids in broth tend to support rather than disrupt the fasted state. Stricter interpretations of fasting exclude bone broth; more pragmatic interpretations include it.

Disputed but generally acceptable:

• Coconut oil or MCT oil (small amounts, less than 1 tsp): Some practitioners use small amounts to accelerate ketone production or sustain energy. Technically breaks autophagy by providing calories; doesn’t disrupt ketosis. Use only if helpful; not necessary.
• Cinnamon, ginger, turmeric in water or tea: Trace calories, supportive compounds.
• Stevia: Of the artificial sweeteners, has the clearest evidence of not raising insulin. Use sparingly if at all.

Avoid:

• Artificial sweeteners (sucralose, aspartame, acesulfame-K, saccharin): Mixed evidence on insulin effects but consistent evidence of negative microbiome effects. Better avoided during fasting.
• Diet sodas: Combine artificial sweeteners with phosphates and other compounds that can disrupt various aspects of the fasted state.
• Bulletproof coffee (coffee with butter and MCT oil): Provides substantial calories. Maintains ketosis but disrupts autophagy and breaks the fast in any meaningful sense. Useful as a low-insulin breakfast, but it isn’t fasting.
• Protein shakes: Break the fast definitively. Reserve for the Targeted Intermittent Fasting protocol where used intentionally for training support.
• Fruit juice, even small amounts: Substantial glucose, breaks fast immediately.
• Caloric beverages of any kind: If it has calories, it breaks the fast.

Electrolyte Management

This is the single most practically important section for anyone doing fasts beyond 24 hours. Most “fasting feels terrible” experiences trace to inadequate electrolyte management.

The mechanism: During fasting, low insulin levels cause the kidneys to excrete more sodium. Glycogen depletion causes water loss (glycogen binds 3x its weight in water). The combination produces substantial sodium, potassium, and magnesium losses that produce the headaches, fatigue, muscle cramps, low blood pressure, and irritability that mark poorly-managed fasting.

Daily electrolyte targets during fasting:

• Sodium: 2,000-3,000 mg minimum, up to 4,000-5,000 mg for very active or sweating individuals. This is substantially more than typical recommendations for fed states.
• Potassium: 1,000-2,000 mg. Less critical than sodium during short-term fasting because cellular potassium stores are substantial.
• Magnesium: 300-500 mg. Many people are deficient at baseline; magnesium glycinate or threonate are well-absorbed forms.
• Calcium: Usually not needed for short fasts; bone stores are substantial.
• Other: Phosphorus and chloride generally don’t require attention for fasts under 5-7 days.

Practical electrolyte protocol:

Morning:

• 1 cup water with 1/4 teaspoon sea salt
• Optional: pinch of “lite salt” or potassium chloride for additional potassium
• Optional: 200-400 mg magnesium glycinate

Midday:

• Salt water (1/4 tsp sea salt in water), or
• Mineral water, or
• 1 cup water with 1-2 tablespoons apple cider vinegar plus pinch of salt

Afternoon (optional):

• Repeat morning protocol if feeling depleted

Evening:

• Salt water before bed if needed
• Optional: another 200-400 mg magnesium glycinate (also supports sleep)

Don’t drink too much water during fasting: This counterintuitive advice traces to a real mechanism: excessive water without electrolytes causes urination of remaining electrolytes, accelerating depletion. Symptoms of hyponatremia (low sodium from excess water) mimic the symptoms of dehydration but require different treatment.

Practical guideline: drink to thirst, not to schedule. Monitor urine colour: pale yellow is the target. Very dark suggests dehydration; completely clear suggests overhydration.

Baking soda for sodium and pH balance:

1/4 to 1/2 teaspoon of baking soda in water provides 600-1,250 mg sodium and supports a slightly alkaline pH balance. Some practitioners use this once or twice per day during longer fasts. Avoid around meal times when eating (would interfere with stomach acid).

Apple cider vinegar:

1-2 tablespoons in water 1-2 times per day. Provides trace potassium, may support blood sugar stability, and may reduce hunger. Use the distilled version (without “the mother”) during fasting to minimise calories; can use unfiltered with mother when refeeding.

Pre-fast preparation:

The day before starting a longer fast, increase sodium and water intake. Adequate “mineral loading” makes the transition smoother. Eat plenty of vegetables, add salt to food, and hydrate well.

Breaking a Fast

The most practically important detail after electrolyte management. Breaking a fast incorrectly produces more discomfort than the fast itself and can be medically dangerous after extended fasts.

General principles:

• The longer the fast, the more cautious the refeed
• Start with easily digestible foods
• Avoid carbohydrates initially (will spike insulin substantially after fasting)
• Avoid large portions (the digestive system has reduced capacity)
• Wait 30-60 minutes between initial small intake and first meal
• Build up to normal eating over hours to days, depending on fast duration

Breaking a 16-24 hour fast:

Simple. Eat your first meal normally. Most people don’t need special protocols here.

Optimal first meal composition:

• Adequate protein (20-30g)
• Healthy fats
• Vegetables
• Avoid large carbohydrate loads (will produce blood sugar spike)
• Avoid heavily processed foods

Breaking a 24-48 hour fast:

Some attention to refeeding helpful.

Step 1 (the moment of breaking):

• 1 cup hot water with juice of half a lemon
• 1-2 tablespoons apple cider vinegar (optional)
• Pinch of salt
• Wait 15-30 minutes

Step 2 (first food):

• Small meal (~500 calories)
• 2-3 eggs, or a small piece of fatty fish, or small portion of bone broth-based soup
• Half an avocado
• Small portion of cooked vegetables
• Avoid raw vegetables, large portions, heavy red meat

Step 3 (later in the day):

• Slightly larger second meal if appetite has returned
• Continue with quality whole foods
• Avoid grains, sugars, and processed foods for the first 24 hours

Breaking a 3-5 day fast:

Substantial care required.

Hour 0:

• 6-8 oz bone broth or
• Hot water with apple cider vinegar and lemon
• Wait 30-60 minutes

Hour 1:

• Small serving of fermented food (2-3 spoonfuls sauerkraut or kimchi)
• Or small portion of bone broth-based soup
• Wait another 30-60 minutes

Hour 2-3:

• First small actual meal (~500 calories)
• 2-3 eggs with avocado, or small piece of fatty fish, or small portion of cooked vegetables with healthy fat
• Eat slowly; chew thoroughly

Hours 4-6:

• Light second meal if appetite has returned
• Continue with easily digestible whole foods

Day 2 of refeeding:

• Slightly more substantial eating
• Still emphasising easily digestible proteins, cooked vegetables, healthy fats
• Avoid grains, sugars, large portions of red meat

Days 2-3:

• Gradual return to normal eating
• Continue prioritising whole foods

Breaking a 5+ day fast:

Substantial caution required because of refeeding syndrome risk. Consider medical guidance if it’s your first extended fast.

The first 24 hours of refeeding are particularly important:

• Multiple small meals rather than fewer large ones
• Continue electrolyte intake (potassium, phosphorus, magnesium needs increase)
• Don’t go straight to high-carbohydrate meals
• Monitor for warning signs (weakness, palpitations, confusion, swelling)

Bone broth is your friend:

Bone broth deserves particular mention because it works exceptionally well for breaking fasts. The combination of:

• Electrolytes (sodium, potassium, magnesium)
• Collagen and gelatin (easy on digestion, gut-supportive)
• Amino acids (glycine, proline) that support healing
• Modest calories that don’t spike insulin
• Warmth that’s soothing after extended fasting

Makes it close to optimal as a fast-breaking food. A 6-8 oz cup followed by 30-60 minutes wait is the practitioner’s default.

Common Mistakes

• Breaking with carbohydrates: Carbohydrates after extended fasting produce substantial insulin spike, blood sugar surge, and gastrointestinal discomfort. Avoid for the first 24 hours of refeeding after extended fasts.
• Drinking too much water without electrolytes: Produces hyponatremia and depletion of remaining electrolytes. Drink to thirst, supplement sodium adequately.
• Inadequate sodium: The most common single mistake. Most people undersalt during fasting because they’re used to normal-eating sodium recommendations. During fasting, increase sodium substantially.
• Aggressive exercise during longer fasts: Body’s stress response is already elevated; adding aggressive training produces excessive cortisol and can disrupt the fasting benefits. Walking and light movement are fine; high-intensity training should wait until you’re refed.
• Starting too aggressive: Going from no fasting practice directly to 5-day water fasts produces miserable experiences and high quit rates. Build up gradually.
• Continuing through warning signs: Persistent dizziness, heart palpitations, confusion, severe weakness are signals to break the fast and refeed, not to push through.
• Treating fasting as a license for poor refeeding: The metabolic benefits depend on what you do during eating windows as much as during fasting periods.
• Fasting through illness or major life stress: Adding fasting stress to existing physiological burden produces worse outcomes than backing off.

Quick Reference Tables

Fasting duration and typical effects:

(BHB values approximate for healthy adults; substantial individual variation.)

Suggested fasting frequency by protocol:

Electrolyte target ranges during fasting (per day):

What to drink while fasting: