Last Updated: November 21, 2025
Popular IF Protocols
| Protocol | Description |
|---|---|
| 16:8 (Leangains) |
16 hours fasting, 8-hour eating window (e.g., noon-8pm)
|
| 18:6 |
18 hours fasting, 6-hour eating window (e.g., 2pm-8pm)
|
| 20:4 (Warrior Diet) |
20 hours fasting, 4-hour eating window (e.g., 4pm-8pm)
|
| OMAD (23:1) |
One meal a day - 23 hours fasting, 1-hour eating window
|
| 5:2 Diet |
Eat normally 5 days, restrict to 500-600 calories 2 non-consecutive days
|
| Alternate Day Fasting |
Alternate between fasting days (0-500 cal) and eating days
|
| Eat-Stop-Eat |
24-hour fast once or twice per week
|
| Crescendo Method |
Fasting 12-16 hours on 2-3 non-consecutive days (for women)
|
16:8 Protocol - Most Popular
| Aspect | Details |
|---|---|
| Fasting window |
16 consecutive hours (usually includes sleep)
|
| Eating window |
8 hours - choose time that fits your schedule
|
| Common schedules |
Noon-8pm, 1pm-9pm, 10am-6pm, 2pm-10pm
|
| Meals per day |
Typically 2-3 meals within window
|
| Difficulty level |
Beginner-friendly - easiest to maintain long-term
|
| Best for |
Daily routine, sustainable lifestyle, beginners
|
| Skip which meal |
Usually breakfast (most common) or dinner
|
5:2 Diet Protocol
| Day Type | Calorie Intake |
|---|---|
| Normal days (5) |
Eat regular healthy diet - no calorie restriction
|
| Fasting days (2) |
Men: 600 calories | Women: 500 calories
|
| Fasting day schedule |
Non-consecutive (e.g., Monday & Thursday)
|
| Meal timing on fast days |
Split calories: 250 cal breakfast, 250 cal dinner OR one 500-600 cal meal
|
| Best for |
People who want flexibility most days, prefer weekly restriction
|
OMAD (One Meal A Day)
| Aspect | Details |
|---|---|
| Eating window |
1 hour, usually same time daily (e.g., 6pm-7pm)
|
| Fasting period |
23 hours
|
| Meal size |
One large meal containing full daily calorie needs
|
| Difficulty level |
Advanced - requires adaptation period
|
| Benefits |
Maximum autophagy, simplicity, time-saving
|
| Challenges |
Getting enough nutrients in one meal, social situations
|
| Best for |
Experienced fasters, busy schedules, aggressive fat loss goals
|
Health Benefits (Evidence-Based)
| Benefit | How IF Helps |
|---|---|
| Weight loss |
Calorie restriction + increased fat oxidation during fasting
|
| Insulin sensitivity |
Lower insulin levels during fasting improve insulin response
|
| Cellular repair (Autophagy) |
Body removes damaged cells and proteins (starts ~16-24 hours)
|
| Brain health |
Increases BDNF (brain-derived neurotrophic factor)
|
| Inflammation reduction |
Lower inflammatory markers
|
| Heart health |
Improved cholesterol, blood pressure, triglycerides
|
| Longevity |
May extend lifespan (studies in animals)
|
| HGH production |
Human growth hormone increases (aids fat loss, muscle gain)
|
What Breaks a Fast
| Item | Breaks Fast? |
|---|---|
| Water |
No - drink freely
|
| Black coffee |
No - under 5 calories
|
| Plain tea (unsweetened) |
No - herbal, green, black tea OK
|
| Coffee with cream/milk |
Yes - contains calories and protein
|
| Sugar/sweeteners |
Yes - triggers insulin response
|
| Zero-calorie drinks |
Debated - may trigger insulin in some people
|
| Apple cider vinegar |
No (small amount) - less than 1 tbsp
|
| Bone broth |
Yes - contains protein and calories
|
| Lemon water |
No - minimal calories (squeeze of lemon)
|
| Gum (sugar-free) |
Technically yes - may trigger cravings/insulin
|
| BCAAs / protein powder |
Yes - protein triggers metabolic response
|
Optimal Meal Timing & Composition
| Meal | Recommendations |
|---|---|
| First meal (break fast) |
Protein + healthy fats + fiber (avoids blood sugar spike)
|
| Protein priority |
0.7-1g per lb bodyweight daily (muscle preservation)
|
| Carb timing |
Later in eating window (promotes better sleep)
|
| Fiber intake |
25-35g daily (satiety and gut health)
|
| Healthy fats |
Avocado, nuts, olive oil, fatty fish (hormone production)
|
| Hydration |
Half bodyweight in oz (e.g., 150 lb = 75 oz water)
|
| Electrolytes |
Sodium, potassium, magnesium (especially on longer fasts)
|
What to Eat During Eating Window
| Food Category | Best Choices |
|---|---|
| Proteins |
Eggs, chicken, fish, Greek yogurt, lean beef, tofu
|
| Healthy fats |
Avocado, olive oil, nuts, seeds, fatty fish (salmon)
|
| Complex carbs |
Quinoa, sweet potato, oats, brown rice, legumes
|
| Vegetables |
Leafy greens, broccoli, cauliflower, peppers, Brussels sprouts
|
| Fruits |
Berries, apples, oranges (moderate portions)
|
| Hydration |
Water, herbal tea, sparkling water, coconut water
|
Foods to Avoid
| Category | Why Avoid |
|---|---|
| Processed foods |
High calories, low nutrition, blood sugar spikes
|
| Sugary drinks |
Empty calories, insulin spike, no satiety
|
| Refined carbs |
White bread, pasta, pastries - rapid blood sugar changes
|
| Trans fats |
Inflammation, heart health risks
|
| Excessive alcohol |
Dehydration, empty calories, impaired fat burning
|
| High-sugar fruits |
In excess - can spike blood sugar (mangoes, grapes)
|
Managing Hunger & Side Effects
| Issue | Solution |
|---|---|
| Initial hunger |
Drink water, black coffee, or tea. Hunger comes in waves - wait 15 min
|
| Headaches |
Often electrolyte deficiency - add pinch of salt to water
|
| Low energy |
Normal at first - body adapting. Usually resolves in 1-2 weeks
|
| Difficulty sleeping |
Eat carbs in evening, avoid late caffeine, maintain schedule
|
| Irritability |
Stay hydrated, get enough sleep, adapt gradually (start with 12:12)
|
| Overeating in window |
Plan meals, eat slowly, focus on protein & fiber first
|
| Social challenges |
Adjust eating window for events, communicate with friends/family
|
Who Should NOT Do IF
| Group | Reason |
|---|---|
| Pregnant/breastfeeding |
Increased caloric and nutrient needs
|
| Children & teens |
Growing bodies need consistent nutrition
|
| History of eating disorders |
May trigger unhealthy relationship with food
|
| Type 1 diabetes |
Blood sugar management challenges
|
| Underweight individuals |
Risk of further weight loss
|
| Certain medications |
Some require food - consult doctor
|
| Chronic stress/adrenal fatigue |
Additional stress on body
|
Starting IF - Week-by-Week Guide
| Week | Protocol |
|---|---|
| Week 1-2 |
12:12 - Ease in with 12-hour fast (8pm-8am)
|
| Week 3-4 |
14:10 - Extend to 14 hours (8pm-10am)
|
| Week 5+ |
16:8 - Full protocol (8pm-noon or preferred window)
|
| Advanced (optional) |
Experiment with 18:6, 20:4, or OMAD once adapted
|
Exercise & IF
| Type | Timing Recommendation |
|---|---|
| Cardio (light-moderate) |
Fasted or fed - both work well
|
| HIIT / intense cardio |
End of fast or early in eating window for energy
|
| Strength training |
Just before eating window or early in window (protein after)
|
| Yoga / stretching |
Anytime - fasted is fine
|
| Endurance training |
May need fuel - test both fasted and fed states
|
| Post-workout meal |
Within 1-2 hours - protein + carbs for recovery
|
💡 Pro Tips:
- Start gradually - don't jump straight to OMAD if you're new to fasting
- Stay busy during fasting hours - hunger is often boredom in disguise
- Black coffee and green tea can suppress appetite and boost fat burning
- Track your eating window with an app (Zero, Fastic, LIFE Fasting) for accountability
- Electrolytes are crucial on longer fasts - add sea salt to water
- Don't compensate by overeating - still need calorie deficit for weight loss
- Adjust window for social events - IF should enhance life, not restrict it
- Give it at least 3-4 weeks before judging results - body needs time to adapt