Intermittent Fasting Calculator
Calculate your fasting schedule, track autophagy phases, estimate fat loss, and optimize your intermittent fasting protocol for maximum health benefits.
Fasting Protocol
16 hours fasting, 8 hour eating window. Most popular protocol.
Difficulty: Beginner
Fasting Window:
20:00 - 12:00
16 hours
Eating Window:
12:00 - 20:00
8 hours
Your Metrics
Metabolic Analysis & Fat Loss
BMR
1649
cal/day baseline
TDEE
2556
cal/day total
Fasting TDEE
2811
+10% metabolic boost
Daily Fat Loss
32.8g
pure fat oxidation
Weekly Loss
0.23kg
~0.51 lbs
Autophagy & Cellular Benefits
Autophagy Status:
Active Autophagy
Peak cellular recycling
Key Benefits of 16:8 (Leangains):
When You'll Hit Each Metabolic Zone
00:00
Blood sugar & insulin drop
Digestion completes
04:00
Glycogen depletion
Body prepares for fat burning
08:00
Metabolic switching
Shift from glucose to fat
12:00
Fat oxidation peaks
Ketone production begins
20:00 (+1 day)
Autophagy activation
HGH increases 5x
20:00 (+2 days)
Deep autophagy
Immune cell regeneration
20:00 (+3 days)
Stem cell activation
Complete immune reset
Metabolic Timeline
Glycogen depletion begins
Switch to fat burning
Increased lipolysis
Fat breakdown accelerates
Autophagy activation
Cellular cleanup
HGH spike (5x)
Muscle preservation + fat loss
Science of Intermittent Fasting
How Fasting Works
During fasting, your body undergoes several metabolic shifts:
- • 0-4h: Blood sugar and insulin drop, digestion completes
- • 4-8h: Glycogen stores deplete, body prepares for fat burning
- • 8-12h: Shift from glucose to fat as primary fuel (metabolic switching)
- • 12-16h: Fat oxidation peaks, ketone production begins
- • 16-24h: Autophagy activates, HGH increases up to 5x baseline
- • 24-48h: Deep autophagy, immune cell regeneration begins
- • 48-72h: Stem cell activation, complete immune system reset
Autophagy Explained
Autophagy ("self-eating") is your body's cellular recycling program. During fasting:
- • Damaged proteins and organelles are broken down
- • Cellular debris is cleared for energy and building blocks
- • Dysfunctional mitochondria are replaced
- • Precancerous cells may be eliminated
- • Inflammation markers decrease significantly
Hormonal Benefits
- • Insulin: Drops 20-31%, improving insulin sensitivity
- • HGH: Increases 300-500%, preserving muscle and burning fat
- • Norepinephrine: Increases metabolic rate 5-14%
- • BDNF: Brain-derived neurotrophic factor increases, enhancing cognition
- • Cortisol: Initially rises (alertness), then normalizes
Safety Guidelines
- ⚠️ Stay hydrated - drink water, electrolytes, black coffee, or tea
- ⚠️ Break fasts gently with easily digestible foods
- ⚠️ Not recommended for pregnant/nursing women, children, or those with eating disorders
- ⚠️ Consult healthcare provider if on medications (especially diabetes meds)
- ⚠️ Extended fasts (24+ hours) should be supervised for first-timers
- ⚠️ Listen to your body - dizziness or extreme weakness = break fast
Medical Disclaimer:
This calculator provides estimates based on scientific research but is not medical advice. Consult healthcare professionals before starting any fasting regimen, especially if you have medical conditions, take medications, or have a history of eating disorders.