Fasting & Seasons

Look around the natural world and one pattern becomes impossible to ignore.

Everything changes with the seasons.

Trees shed their leaves before growing them again. Birds migrate across continents. Mammals grow thicker coats for winter and shed them in spring. Some animals hibernate for months, while others dramatically alter their behaviour, metabolism, reproduction, and energy use depending on the time of year. We look at the extreme end of that spectrum in Hibernation.

Nature does not operate in a constant state.

It operates in cycles.

Humans often assume we are different—that we have escaped the influence of the seasons through technology, central heating, supermarkets, refrigeration, and artificial lighting. Yet growing scientific evidence suggests that our biology still responds to many of the same environmental cues that shaped our ancestors for hundreds of thousands of years.

One of those cues may be fasting.

Nature Speaks Through Signals

The environment constantly provides information to every living organism.

The changing temperature tells plants when to flower.

Rainfall determines when seeds germinate.

Tides influence marine life.

And perhaps the most reliable signal of all is the changing length of the day.

Scientists call this photoperiod—the number of hours of daylight received over a 24-hour period.

Unlike temperature, which can fluctuate from one day to the next, photoperiod changes with remarkable precision throughout the year. For countless species, it acts as nature's calendar. We explore the daily version of this signal in Fasting & Sunlight.

As the days shorten or lengthen, animals adjust their physiology in preparation for what lies ahead.

Photoperiod: Nature's Calendar

Many mammals don't simply react to winter after it arrives.

They prepare for it weeks or even months in advance.

Shortening daylight triggers hormonal changes that can lead to:

• Increased fat storage
• Changes in appetite
• Altered metabolism
• Thicker fur
• Reduced reproductive activity
• Shifts in immune function
• Lower energy expenditure
• Hibernation or torpor in some species

Remarkably, these animals do not change their genes.

Instead, they express different characteristics from the same genetic blueprint.

Biologists call this phenotypic plasticity—the ability of one organism to display different physical or physiological traits in response to its environment.

In other words, the environment doesn't rewrite the genetic code. It changes how that code is expressed.

Do Humans Have Seasonal Phenotypes?

Humans do not undergo dramatic seasonal transformations like Arctic foxes or bears, but we have not completely escaped our evolutionary heritage.

Research has shown seasonal variations in humans affecting:

• Melatonin production
• Sleep patterns
• Mood
• Immune activity
• Vitamin D levels
• Hormone timing
• Physical activity
• Brown fat activation
• Metabolic function

These changes are generally subtle, but they suggest that our bodies still recognise the changing seasons, even if modern life often masks their effects.

Rather than having a single "optimal" physiology, it is possible that humans evolved to shift gently between different physiological states throughout the year.

The Summer and Winter Body

Imagine two versions of the human body.

Not different people—but different biological modes.

A summer phenotype might be characterised by:

• Longer daylight
• Greater food availability
• Higher physical activity
• Growth and reproduction
• Building muscle and storing energy
• Increased social interaction

A winter phenotype might favour:

• Greater reliance on stored body fat through lipolysis
• Improved metabolic efficiency
• Increased ketosis during food scarcity
• Enhanced cellular maintenance via autophagy
• Conservation of energy
• Reduced investment in growth

Unlike many mammals, humans do not switch dramatically between these states. Yet we may retain elements of these ancient seasonal programmes.

Our biology evolved in an environment where food, light, temperature, and activity all changed together.

Before Supermarkets

Imagine living ten thousand years ago.

There are no refrigerators.

No imported fruit.

No convenience stores.

The amount and type of food available depends entirely on the season.

Some months bring abundance.

Others require patience, skill, and endurance.

Periods of reduced food intake are not unusual—they are inevitable.

At the same time:

• Daylight changes.
• Temperatures fluctuate.
• Sleep patterns shift.
• Physical activity varies.
• Food quality changes.

The body receives many environmental messages at once.

Fasting Is More Than Missing Meals

We often ask:

"What does fasting do?"

Perhaps a better question is:

"What information does fasting give the body?"

Throughout evolution, fasting rarely occurred in isolation.

It usually coincided with changing seasons, longer nights, colder weather, greater physical effort, and reduced food availability.

To the brain, fasting may have acted as an environmental message:

• Food is less abundant.
• Use stored energy wisely.
• Become more metabolically efficient.
• Prioritise maintenance over growth.
• Increase resilience.

Viewed this way, fasting is not simply the absence of food—it is a signal that helps the body adapt to changing conditions.

The Missing Environmental Signals

Modern life has transformed nearly every cue our ancestors once relied upon.

Many of us experience:

• Artificial lighting from dawn until midnight
• Climate-controlled homes throughout the year
• Constant access to food
• Minimal seasonal variation in diet
• Sedentary work regardless of the weather
• Similar routines every month of the year

Our bodies evolved expecting seasons.

Instead, many of us now experience a perpetual, climate-controlled version of summer.

While this has brought enormous benefits in comfort, safety, and food security, it has also removed many of the natural signals that once helped regulate human physiology.

Fasting as an Ancient Signal

Fasting may be one of the few ancestral environmental cues that we can deliberately reintroduce.

It reminds the body that resources are not always unlimited.

It encourages metabolic flexibility.

It activates pathways involved in repair, recycling, and adaptation.

Rather than viewing fasting solely as a weight-loss strategy, it may be more accurate to see it as one piece of an environmental language that the human body has understood for millennia. A similar argument underpins Fasting & Earthing.

Light, movement, temperature, social connection, sleep, and food availability all contribute to that language.

Fasting is simply one of its oldest words.

The One Year Fast Perspective

The One Year Fast is not an attempt to recreate the hardships of prehistoric life.

Modern medicine, sanitation, agriculture, and food security have transformed human wellbeing for the better.

Instead, the project asks a different question:

What aspects of our ancient environment are still important for modern health?

Seasonal change shaped every generation that came before us.

The length of the day influenced hormones.

The availability of food influenced metabolism.

Periods of scarcity encouraged resilience.

Nature continually asked the body to adapt.

Perhaps our greatest challenge today is not that we experience too many seasons—but too few.

By introducing periods of voluntary fasting into a life of constant abundance, we may be restoring one of the environmental signals that human biology evolved to recognise.

The seasons still change.

The sun still rises and sets.

Our genes still carry the memory of the world in which they evolved.

Fasting may simply be one way of listening to that ancient conversation once again.