Intermittent Fasting: Complete Beginner's Guide
Learn everything about intermittent fasting—methods, benefits, weight loss potential, and how to start safely. Science-backed information for beginners.
What is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. It doesn't specify which foods to eat, but rather when you should eat them. It's not a diet in the traditional sense—it's more accurately described as an eating schedule.
Humans have fasted throughout history. Our hunter-gatherer ancestors didn't have supermarkets or refrigerators. Sometimes they couldn't find food, so our bodies evolved to function without food for extended periods.
Fasting from time to time is more natural than eating 3-4+ meals every single day. During fasting, your body initiates cellular repair processes and changes hormone levels to make stored body fat more accessible.
Popular Intermittent Fasting Methods
There are several different ways to do intermittent fasting. Here are the most popular methods:
16:8 Method (Leangains)
Fast for 16 hours, eat within an 8-hour window. Most popular and beginner-friendly.
Example: Eat from 12pm to 8pm, fast from 8pm to 12pm next day.
Difficulty: Easy — Skip breakfast, eat lunch and dinner
18:6 Method
Fast for 18 hours, eat within a 6-hour window. More aggressive than 16:8.
Example: Eat from 1pm to 7pm only.
Difficulty: Moderate — Requires more discipline
5:2 Diet
Eat normally 5 days per week, restrict calories to 500-600 on 2 non-consecutive days.
Example: Eat normal Monday-Friday, restrict calories Saturday and Wednesday.
Difficulty: Moderate — Full-day restriction can be challenging
Eat-Stop-Eat (24-Hour Fasts)
Complete 24-hour fast once or twice per week.
Example: Dinner Monday, don't eat until dinner Tuesday.
Difficulty: Hard — Full 24 hours without food is challenging
OMAD (One Meal A Day)
Eat all daily calories in one meal, fast for ~23 hours.
Example: Only eat dinner each day.
Difficulty: Very Hard — Not recommended for beginners
🎯 Recommendation for Beginners:
Start with 16:8. It's the easiest to maintain, most researched, and delivers excellent results without extreme restriction.
Health Benefits of Intermittent Fasting
Research shows intermittent fasting has numerous benefits beyond weight loss:
Weight Loss & Fat Burning
IF naturally reduces calorie intake and enhances fat burning through hormonal changes. Lower insulin levels make stored body fat more accessible as fuel.
Improved Insulin Sensitivity
Fasting lowers blood sugar by 3-6% and fasting insulin by 20-31%. This reduces risk of type 2 diabetes.
Cellular Repair (Autophagy)
Fasting triggers autophagy—your body's cellular cleanup process. Old, dysfunctional proteins are removed and recycled.
Brain Health
IF increases brain-derived neurotrophic factor (BDNF), which supports brain function and may reduce risk of Alzheimer's and depression.
Heart Health
Studies show IF can reduce LDL cholesterol, blood triglycerides, inflammation markers, and blood pressure.
Increased Human Growth Hormone
Fasting can increase HGH by up to 5x, which aids fat burning and muscle gain.
Reduced Inflammation
Some studies show reduced markers of inflammation, a key driver of many chronic diseases.
Simplicity
Fewer meals to plan, prepare, and clean up. Many people find IF simplifies their daily routine.
Intermittent Fasting for Weight Loss
The main reason people try intermittent fasting is to lose weight. Here's how it works:
How IF Promotes Weight Loss:
- 1. Calorie Reduction: Eating fewer meals naturally reduces total calorie intake (unless you compensate by eating much more)
- 2. Lower Insulin: Fasting lowers insulin, which allows fat cells to release stored fat for energy
- 3. Increased Norepinephrine: Fasting increases norepinephrine, which boosts metabolism and fat burning
- 4. Higher HGH: Growth hormone increases during fasting, preserving muscle while burning fat
Expected Weight Loss Results:
| Timeframe | Expected Loss | Notes |
|---|---|---|
| Week 1-2 | 3-7 lbs | Mostly water weight |
| Month 1 | 4-8 lbs | Fat loss begins |
| Month 2-3 | 8-16 lbs | Steady fat loss |
| 6 Months | 15-30 lbs | Sustainable results |
⚠️ Important:
IF is not magic. Weight loss still requires a calorie deficit. If you overeat during your eating window, you won't lose weight. IF just makes it easier to eat less naturally.
How to Start Intermittent Fasting Safely
Starting IF is simple, but doing it right maximizes results and minimizes discomfort:
Step-by-Step Guide:
- 1. Choose Your Method: Start with 16:8 (skip breakfast, eat lunch and dinner). It's the easiest.
- 2. Pick Your Eating Window: Most people choose 12pm-8pm, but adjust to your schedule.
- 3. Start Gradually: Begin with 12:12 for a few days, then progress to 14:10, then 16:8.
- 4. Stay Hydrated: Drink water, black coffee, and unsweetened tea during fasting periods.
- 5. Eat Nutritious Foods: Don't use IF as an excuse to eat junk. Focus on protein, vegetables, healthy fats.
- 6. Be Patient: The first week is hardest. Hunger usually subsides after 3-7 days.
- 7. Listen to Your Body: If you feel unwell, eat something. Don't push through severe symptoms.
What Breaks a Fast?
✅ OK During Fasting:
- • Water (plain or sparkling)
- • Black coffee (no sugar/cream)
- • Plain tea
- • Salt/electrolytes
- • Zero-calorie drinks (debated)
❌ Breaks Your Fast:
- • Any food
- • Coffee with cream/sugar
- • Milk or dairy
- • Fruit juice
- • Bone broth (small exception)
Who Should NOT Try Intermittent Fasting?
IF is safe for most healthy adults, but certain groups should avoid it or consult a doctor first:
Calculate Your Calorie Needs for IF
To maximize IF results, know your calorie target. Use our calculator to find your maintenance and weight loss calories.
Calculate Your Calories →