Published by Paul Thompson |
Fact-checked against peer-reviewed sources | Updated March 2026
FREE LONGEVITY GUIDE

# Intermittent Fasting
for Longevity

Unlock Autophagy & Extend Your Healthspan

By Longevity Futures Research Team

## Chapter 1: What Is Intermittent Fasting?

Intermittent fasting (IF) isn't about what you eat - it's about when you eat. By cycling between periods of eating and fasting, you trigger powerful cellular processes that promote longevity.

The Science: After 12-16 hours without food, your body shifts from using glucose for energy to burning fat and producing ketones. This metabolic switch activates autophagy - your body's cellular cleanup system.

### Key Benefits for Longevity

- Autophagy: Cellular cleanup that removes damaged proteins and organelles
- Insulin Sensitivity: Improved blood sugar regulation
- Fat Loss: Enhanced fat burning without muscle loss
- Brain Health: Increased BDNF (brain growth factor)
- Inflammation: Reduced inflammatory markers
- Longevity Genes: Activates sirtuins and AMPK pathways

Nobel Prize Winner: In 2016, Yoshinori Ohsumi won the Nobel Prize for his discoveries on autophagy mechanisms - the same cellular process activated by fasting.

## Chapter 2: Fasting Protocols Explained

There's no "best" protocol - the right one is the one you can stick with. Here are the most popular methods:

16:8 Method

#### The Most Popular

Fast for 16 hours, eat within an 8-hour window. Example: Eat from 12pm-8pm, fast from 8pm-12pm.

Best for: Beginners, daily practice, sustainable lifestyle

18:6 Method

#### Enhanced Autophagy

Fast for 18 hours, eat within a 6-hour window. Example: Eat from 1pm-7pm only.

Best for: Intermediate fasters, deeper autophagy

OMAD

#### One Meal A Day

Eat one large meal within a 1-2 hour window. Fast the remaining 22-23 hours.

Best for: Advanced fasters, maximum autophagy

5:2 Method

#### Weekly Approach

Eat normally 5 days per week. On 2 non-consecutive days, limit calories to 500-600.

Best for: Those who prefer less frequent fasting

### Choosing Your Protocol

- New to fasting? Start with 14:10, then progress to 16:8
- Want fat loss? 16:8 or 18:6 works well
- Maximum autophagy? Try 24-hour fasts once weekly
- Busy schedule? OMAD simplifies meal planning

## Chapter 3: What Happens During a Fast

Understanding the timeline helps you appreciate why fasting works:

#### 0-4 Hours: Fed State

Blood sugar rises, insulin is released, body stores energy. No fasting benefits yet.

#### 4-8 Hours: Early Fasting

Blood sugar normalizes, insulin drops. Body starts using stored glycogen.

#### 8-12 Hours: Glycogen Depletion

Liver glycogen depletes. Body begins transitioning to fat burning.

#### 12-16 Hours: Fat Burning & Ketosis

Fat burning accelerates. Ketone production begins. Autophagy starts ramping up.

#### 16-24 Hours: Deep Autophagy

Significant autophagy. Growth hormone increases 5x. Maximum cellular cleanup.

#### 24-48 Hours: Enhanced Benefits

Peak autophagy. Immune system regeneration begins. Not recommended for beginners.

Key Insight: Most longevity benefits kick in around the 16-hour mark. That's why 16:8 is so effective - you get the benefits without extreme deprivation.

## Chapter 4: How To Start Fasting

### Week 1: The Adjustment Phase

- Start with 12:12 (12-hour eating window)
- Stop eating after dinner (e.g., 8pm)
- Delay breakfast slightly (e.g., 8am)
- Drink plenty of water, black coffee, or tea

### Week 2: Extend Your Fast

- Move to 14:10 (push breakfast to 10am)
- Your hunger hormones will begin adjusting
- Notice: morning hunger often disappears by itself

### Week 3: Reach 16:8

- Skip breakfast entirely or delay until noon
- Eat your first meal at 12pm
- Finish eating by 8pm
- You're now doing 16:8!

What to Expect: The first 3-5 days may include hunger, irritability, or brain fog. This is normal! Your body is adapting. These symptoms disappear within 1-2 weeks.

### What Breaks a Fast?

These are OK during fasting:

- Water (plain or sparkling)
- Black coffee (no sugar, no cream)
- Plain tea (green, black, herbal)
- Salt or electrolytes (important!)

These break your fast:

- Any calories (food, juice, smoothies)
- Cream, milk, or sugar in coffee
- Diet sodas (artificial sweeteners may spike insulin)
- Bone broth (contains protein)

## Chapter 5: Fasting-Friendly Supplements

Certain supplements can enhance your fast without breaking it:

### Electrolytes (Essential)

During fasting, you excrete more sodium, potassium, and magnesium. Replenishing these prevents headaches, fatigue, and cramps.

#### LMNT Electrolyte Powder

Zero sugar, zero calories - perfect for fasting

Shop on Amazon

Affiliate link

### Coffee (Enhances Fasting)

Black coffee actually enhances autophagy and fat burning. It also suppresses hunger.

### Fasting-Safe Supplements

- Magnesium: Won't break fast, helps with sleep and cramping
- Vitamin D: Fat-soluble, best taken with food but won't break fast
- Fish Oil: Contains calories - take with your first meal
- NMN/NR: May enhance fasting benefits, taken in morning

#### Thorne Magnesium Bisglycinate

Highly absorbable magnesium for sleep, relaxation & recovery - take before bed

~$28 on Amazon

Affiliate link

#### ProHealth NMN Pro 1000

NAD+ precursor - synergizes with fasting for longevity

~$70 on Amazon

Affiliate link

## Chapter 6: Breaking Your Fast Right

How you break your fast matters, especially for longer fasts (18+ hours).

### Best Foods to Break a Fast

- Bone broth or soup: Gentle, nutrient-dense, easy to digest
- Eggs: Protein-rich, won't spike blood sugar
- Avocado: Healthy fats, easy on stomach
- Vegetables: Fiber, nutrients, low insulin response
- Protein: Chicken, fish, or plant protein

### Foods to Avoid When Breaking Fast

- Sugar and sweets: Blood sugar spike after fasting
- Processed carbs: Bread, pasta, white rice
- Large portions: Start small, give digestive system time
- Fried foods: Hard to digest after fasting

Pro Tip: For 16:8 fasting, you don't need to be as careful. But for 24+ hour fasts, always break with something light and protein-rich.

### Sample Break-Fast Meals

- Option 1: 2 scrambled eggs + avocado + sauteed spinach
- Option 2: Greek yogurt + berries + nuts
- Option 3: Grilled chicken salad with olive oil dressing
- Option 4: Salmon + roasted vegetables

## Chapter 7: Common Fasting Mistakes

### Mistake 1: Not Drinking Enough Water

You're not eating food that contains water, so you need to drink more. Aim for 2-3 liters during fasting hours.

### Mistake 2: Ignoring Electrolytes

Headaches, fatigue, and cramps during fasting are usually electrolyte deficiency, not hunger. Add salt to water or use electrolyte powder.

### Mistake 3: Overeating When Breaking Fast

Your eating window isn't a "free for all." Eat until satisfied, not stuffed. Quality still matters.

### Mistake 4: Starting Too Aggressive

Jumping straight into 24-hour fasts sets you up for failure. Build up gradually over weeks.

### Mistake 5: Fasting Every Day Forever

Some experts recommend cycling your fasting schedule. Consider taking weekends off or varying your fasting hours.

Who Should NOT Fast:

- Pregnant or breastfeeding women
- People with eating disorder history
- Type 1 diabetics (without medical supervision)
- Underweight individuals
- Children and teenagers

Always consult your doctor before starting any fasting protocol.

## Chapter 8: Advanced Fasting Strategies

### Extended Fasting (24-72 Hours)

For maximum autophagy, some practice occasional extended fasts:

- 24-hour fast: Once per week or month
- 36-hour fast: Dinner to breakfast the next day
- 72-hour fast: Quarterly for deep cellular reset

Extended fasts require more preparation and should be done under guidance if new to fasting.

### Fasting Mimicking Diet (FMD)

Developed by Dr. Valter Longo, this is a 5-day low-calorie protocol that triggers fasting benefits while still eating small amounts. Good for those who can't fully fast.

### Fasting + Exercise

- Light cardio: Safe during fasting, may enhance fat burning
- Strength training: Best done near your eating window
- High intensity: Save for fed state, or at least have protein after

### Fasting + Longevity Supplements

Combine fasting with supplements that work on similar pathways:

- Resveratrol + Fasting: Both activate sirtuins
- NMN + Fasting: Both boost NAD+ levels
- Berberine + Fasting: Both activate AMPK

#### ProHealth Trans-Resveratrol 1000mg

Sirtuin activator - synergizes with fasting

~$45 on Amazon

Affiliate link

## Start Your Fasting Journey

Intermittent fasting is one of the most powerful, free, and accessible longevity interventions available. Start with 16:8, be patient with the adjustment period, and enjoy the benefits.

Your cells are waiting to clean house!

More free longevity guides at:

longevityfutures.online/diets