Intermittent Fasting Calculator 2026

Choose the IF protocol that fits your lifestyle and experience level. ### Protocol Comparison Table | Protocol | Fasting Hours | Eating Window | Difficulty | Best For | Weight Loss Potential | |----------|---------------|---------------|------------|----------|----------------------| | **12:12** | 12 | 12 hours | Beginner | Starting IF, metabolic health | Low-Moderate | | **14:10** | 14 | 10 hours | Beginner | Women, gentle approach | Moderate | | **16:8** | 16 | 8 hours | Intermediate | Most people, sustainable | High | | **18:6** | 18 | 6 hours | Advanced | Experienced fasters | Very High | | **20:4 (Warrior)** | 20 | 4 hours | Very Advanced | Disciplined individuals | Very High | | **OMAD** | 23 | 1 hour | Expert | Maximum autophagy seekers | Very High | | **5:2** | Normal eating | 500-600 cal 2x/week | Intermediate | Flexible schedules | High | | **ADF** | Alternating | 0 or 500 cal every other day | Advanced | Structured routines | Very High | ### Detailed Protocol Breakdown **16:8 Method (Most Popular)** - **Example Schedule:** Eat 12pm-8pm, Fast 8pm-12pm (next day) - **Skipped Meal:** Breakfast - **Pros:** Sustainable long-term, social life-friendly, proven results, autophagy benefits - **Cons:** May be hungry initially (adapts in 1-2 weeks) - **Ideal For:** Busy professionals, athletes, anyone seeking sustainable fat loss **18:6 Method (Advanced)** - **Example Schedule:** Eat 2pm-8pm, Fast 8pm-2pm (next day) - **Skipped Meals:** Breakfast + mid-morning snack - **Pros:** Deeper autophagy, more fat burning, enhanced mental clarity - **Cons:** Requires discipline, social challenges, harder for beginners - **Ideal For:** Experienced fasters, rapid fat loss goals, therapeutic benefits **20:4 Warrior Diet** - **Example Schedule:** Eat 4pm-8pm, Fast 8pm-4pm (next day) - **Skipped Meals:** Breakfast, lunch - **Pros:** Maximum daily fasting benefits, simplified eating, deep autophagy - **Cons:** Very challenging socially, requires planning, not for beginners - **Ideal For:** Disciplined individuals, evening eaters, extreme results **OMAD (One Meal A Day)** - **Example Schedule:** Eat 6pm-7pm, Fast 7pm-6pm (next day) - **Skipped Meals:** Everything except dinner - **Pros:** Ultimate simplicity, maximum autophagy, lowest insulin exposure - **Cons:** Very difficult to meet nutrition needs, social isolation risk, extreme discipline required - **Ideal For:** Experienced fasters, therapeutic fasting, specific health goals - **Warning:** Risk of nutrient deficiency if meal not well-planned **5:2 Diet** - **Schedule:** Eat normally 5 days/week, restrict to 500-600 calories 2 non-consecutive days - **Example:** Normal Mon/Wed/Thu/Fri/Sat, Fast Sun/Tue - **Pros:** Flexible, less daily restriction, proven for weight loss - **Cons:** Fasting days can be brutal, requires willpower on fast days - **Ideal For:** Those who can't do daily fasting, structured schedules ### Progression Path (Beginner → Expert) **Week 1-2:** 12:12 (Ease into fasting, minimal hunger) **Week 3-4:** 14:10 (Build adaptation, see initial results) **Month 2-3:** 16:8 (Sweet spot for most people) **Month 4+:** 18:6 or custom (Advanced benefits if desired) **Optional:** OMAD or 20:4 for specific goals (not necessary for results) **DON'T:** Jump straight to OMAD—sets you up for failure and potential health issues

Autophagy is the primary cellular benefit distinguishing IF from simple calorie restriction. ### What is Autophagy? **Autophagy** (Greek: "self-eating") is your body's cellular recycling and quality control system. During fasting, cells break down and remove: - Damaged proteins - Dysfunctional mitochondria - Misfolded molecules - Cellular debris This isn't destruction—it's **renewal**. Components are recycled into new, healthy cellular material. ### Autophagy Timeline During Fasting | Hours Fasted | Autophagy Level | What's Happening | |--------------|-----------------|------------------| | 0-12 | Minimal | Glucose burning, autophagy baseline | | 12-16 | Beginning | Autophagy genes activating (AMPK pathway) | | 16-18 | Moderate | Visible autophagy increase, cellular cleanup | | 18-24 | High | Peak autophagy for daily fasting, immune renewal | | 24-48 | Very High | Deep autophagy, stem cell activation | | 48-72 | Maximum | Immune system reset, maximum renewal | **Note:** You don't need 72-hour fasts for benefits. Daily 16-18 hour fasts provide significant autophagy. ### Health Benefits Linked to Autophagy **Longevity & Anti-Aging:** - Removal of damaged cellular components slows aging - Reduced oxidative stress and inflammation - Enhanced mitochondrial function (energy production) **Brain Health:** - Clearance of protein aggregates (linked to Alzheimer's, Parkinson's) - Increased BDNF (brain-derived neurotrophic factor) - Improved neuroplasticity and cognitive function - Protection against neurodegenerative diseases **Metabolic Health:** - Improved insulin sensitivity - Enhanced glucose regulation - Reduced risk of type 2 diabetes - Better cholesterol profiles **Cancer Prevention:** - Removal of damaged cells before they become cancerous - Reduced inflammation (cancer fuel) - Enhanced immune surveillance **Immune System:** - Regeneration of immune cells - Reduced chronic inflammation ("inflammaging") - Enhanced pathogen defense ### How to Maximize Autophagy During IF **DO:** - Fast for at least 16 hours (sweet spot: 16-18 hours) - Exercise in fasted state (amplifies autophagy signals) - Drink green tea or black coffee (polyphenols enhance autophagy) - Sleep quality matters (autophagy peaks during sleep) - Manage stress (cortisol inhibits autophagy) **DON'T:** - Break fast with high-sugar foods (stops autophagy immediately) - Overconsume protein (mTOR activation inhibits autophagy) - Stress eating during window (negates benefits) - Snack constantly in eating window (keeps insulin elevated) ### Autophagy vs Calorie Restriction **IF with Autophagy:** - Cellular renewal WHILE eating adequate calories - Preserves muscle mass (HGH spike) - Sustainable long-term - Hormonal benefits intact **Chronic Calorie Restriction:** - Requires constant willpower - May slow metabolism - Muscle loss risk - No concentrated autophagy period **Conclusion:** IF provides autophagy benefits WITHOUT chronic calorie deprivation.

Start smart to ensure long-term success with intermittent fasting. ### Step-by-Step IF Startup Plan **Week 1: 12:12 Protocol (Test the Waters)** - Eating Window: 8am - 8pm - Fasting Window: 8pm - 8am - Goal: Get comfortable with the concept of a fasting window - What to Expect: Minimal hunger (most people naturally do this) **Week 2: 14:10 Protocol (Ease In)** - Eating Window: 10am - 8pm - Fasting Window: 8pm - 10am - Goal: Delay breakfast by 2 hours - What to Expect: Mild morning hunger, easily manageable with coffee/tea **Week 3-4: 16:8 Protocol (The Standard)** - Eating Window: 12pm - 8pm - Fasting Window: 8pm - 12pm - Goal: Skip breakfast entirely, lunch becomes first meal - What to Expect: Day 1-3 = moderate hunger. Day 4-7 = adaptation. Day 8+ = hunger fades **Month 2+: Optimize & Adjust** - Find your ideal eating window timing - Experiment with 18:6 if desired - Lock in eating window consistency ### Choosing Your Eating Window **Option 1: Skip Breakfast (Most Common)** - Eating Window: 12pm - 8pm - Pros: Social dinner times preserved, morning productivity boost - Cons: May feel hungry initially (coffee helps) - Best For: Night eaters, social dinners, busy mornings **Option 2: Skip Dinner (Early Eater)** - Eating Window: 8am - 4pm - Pros: Better sleep (no late eating), align with circadian rhythm - Cons: Social dinners difficult - Best For: Early risers, those with sleep issues, circadian fasting enthusiasts **Option 3: Skip Lunch (Flexible)** - Eating Window: 8am - 12pm + 6pm - 8pm (split window) - Pros: Breakfast AND dinner - Cons: Technically not continuous fasting, less autophagy - Best For: Social situations, family dinners **Recommendation:** 12pm - 8pm window for beginners. Most sustainable, easiest socially. ### First Week Survival Guide **Morning Hunger?** - Drink 16-20oz water immediately upon waking - Black coffee or green tea (appetite suppressant) - Stay busy (hunger comes in waves, passes in 10-20 min) - Remember: Ghrelin (hunger hormone) spikes at "normal" meal times—it will adapt **Energy Crashes?** - Add electrolytes to water (sodium, potassium, magnesium) - Ensure adequate sleep (7-8 hours) - May indicate dehydration, not true hunger - Typically resolves after week 1 **Social Pressure?** - "I'm not hungry yet" works better than "I'm fasting" - Adjust eating window for special occasions (flexibility is key) - Coffee dates replace breakfast dates **Not Losing Weight?** - IF creates eating window, NOT automatic deficit - Still need to be in calorie deficit for fat loss - Track food for 1 week to ensure you're not overeating in window - Be patient: Body composition changes before scale moves ### What to Eat in Your Eating Window **First Meal (Breaking Fast):** - Prioritize protein + healthy fats - Examples: Eggs, avocado, nuts, Greek yogurt, salmon - Avoid: Simple carbs alone, sugary foods (insulin spike) **Meal Distribution (16:8 example):** - 12pm: Lunch (largest meal, 40-50% calories) - 4pm: Snack (optional, 10-20% calories) - 7pm: Dinner (35-40% calories) **Macros:** - Protein: 0.8-1g per lb body weight (prevents muscle loss) - Fats: 25-35% of calories - Carbs: Remaining calories (prioritize whole foods) ### Red Flags to Stop IF - Loss of menstrual cycle (women) - Extreme fatigue beyond week 2 - Binge eating in eating window - Obsessive food thoughts all day - Hair loss, brittle nails **IF should enhance your life, not consume it.** If it causes stress or health issues, it's not for you.