Nov 16, 2025

What’s the BestWhat’s the Best Time of Year to Fast?Time of Year to Fast?

How your biology and your goals should shape your fasting strategy

Most fasting advice assumes you should be in “monk mode” 24/7. Skip breakfast. Shrink your window. Power through. But the truth is far more interesting.

Your biology is seasonal.

Humans evolved according to light cycles, temperature, food availability, and environmental cues. Today most people live in a “permanent summer” of artificial light and constant calories, and their biology is confused. No wonder energy, mood, and metabolism are all over the place.

Here’s how to fast in a way that works with your biology, not against it.

The Myth of “Always Fast”

Fasting can absolutely improve insulin sensitivity, cellular repair, and metabolic health. But fasting is a tool, not an identity. When you push the same lever all year long, you miss half the benefits.

Your body thrives when there is a rhythm between growth and repair, just like nature intended.

🌞 Summer: The Season of Growth

Longer days and stronger sunlight shift your body into performance mode.

• More sunlight increases testosterone, dopamine, and thyroid activity
• More natural carbs help replenish glycogen and support leptin signaling
• More movement boosts recovery and training intensity

Your biology reads these signals as abundance. This is not the season to deprive yourself.

If your goals are:

muscle gain
athletic performance
hormone optimization

Summer fasting should be gentle.

Try:

• A 12 to 14 hour eating window
• High-protein meals
• Seasonal carbs like fruit, roots, and honey
• Plenty of sunlight and hydration

Summer is your anabolic phase.
Feed. Train. Recover. Grow.

❄️ Winter: The Season of Repair

As days shorten and temperatures drop, your metabolism naturally shifts into a slower, restorative mode.

Cold and darkness increase:

• AMPK activation for better energy regulation
• Fat utilization
• Autophagy for cellular cleanup
• Mitochondrial repair

Winter fasting is not just helpful. It is aligned with your biology.

If your goals are:

longevity
inflammation reduction
metabolic cleanup
deep repair

Winter is your perfect window.

Try:

• A 16 to 20 hour fasting window
• Occasional 24 hour fasts
• Lower carb and higher fat meals
• Early nights and darker evenings
• More sauna and cold exposure

Winter is your catabolic phase.
Fast. Reflect. Rebuild.

⚖️ The Balance: Growth vs. Repair

Think of your metabolism like a pendulum.

• Too much fasting leads to muscle loss, sluggish thyroid, and burnout
• Too much eating leads to inflammation, poor glucose control, and faster aging

Health lives in the balance.

• Summer signals mTOR for growth
• Winter signals AMPK for cleanup

You are not hacking your body. You are working with nature.

🌍 A Modern, Realistic Blueprint

You do not need to move to a cave or track sunrise charts. Just follow a simple seasonal pattern.

Winter (Dec to March)

• Fast 16 to 20 hours
• One 24 hour fast weekly if you like
• Lower carb and higher fat meals
• More sleep, sauna, and cold exposure

Spring and Fall (April to May and Sept to Nov)

• Fast 14 to 16 hours
• Mix your macros
• Stay consistent with circadian habits

Summer (June to Aug)

• Fast 12 to 14 hours
• Increase protein and carbs
• Train harder with more outdoor movement
• Maximize sunlight and electrolytes

This is not a diet. This is metabolic seasonality.

🧠 The Big Picture

Fasting is not universally good or bad.
It is contextual.
It is seasonal.
And it should match your goals.

Your biology gives you cues all year long. When you follow them, you unlock better energy, deeper repair, and long-term vitality.

🌅 Final Thought

Health is not just about what you eat.
It is when you eat and why you eat.

Instead of asking “Should I fast”
Try asking “What season am I in”