You are not designed to feel the same all year long, and the fact that your calendar is doesn't change your physiology.
Winter feels inward. Summer feels outward.
Three things shift when the light does. Once you can name them, the January version of yourself stops looking like a personal failing.
Cortisol
Light regulates cortisol. When morning light hits your eyes, cortisol rises and melatonin falls — that's the mechanism that wakes you up, and it's driven by photons, not by willpower.
In winter, cortisol rises more slowly and melatonin carries later into the morning. Which is exactly why getting out of bed in January feels categorically different from June, and why pressing snooze three times doesn't help: you're waiting on a signal that isn't arriving.
The fix is five to ten minutes of morning light exposure, and grey skies still count. Outdoor overcast light is many times brighter than indoor lighting. You don't need sun. You need to be outside, near a window doesn't cut it, and it needs to happen within about an hour of waking.
In summer, cortisol naturally rises earlier. You wake with the light, move easily, feel motivated, and your dopamine thrives. Same body, different input.
Insulin sensitivity
In winter, with light exposure low, cortisol and insulin sensitivity shift together. Your body becomes more reactive to stress than it is in the summer — which changes the maths on anything that adds stress deliberately.
Fasting too long in winter backfires
Skipping meals → more cortisol → worse insulin sensitivity.
In summer, sunlight regulates your cortisol for you. That's why you can skip breakfast, run on an empty stomach and still feel fine. In winter, the same choice costs you more than it returns.
This isn't an argument against fasting. It's an argument that the window that worked in August is the wrong window in January — the seasonal version of the same point the cycle guide makes monthly.
Serotonin
Ever notice how your cravings change in winter? Bread, pasta, soup, chocolate. That's not a collapse of discipline. It's seasonal serotonin.
Reduced daylight lowers brain serotonin activity. To compensate, the body increases its demand for serotonin. Serotonin is synthesised from tryptophan — and tryptophan only crosses efficiently into the brain in the presence of carbohydrates.
When carbs are overly restricted during winter, serotonin production can drop, contributing to low mood and fatigue.
So the winter carb craving is a request with a mechanism behind it. Restricting hardest in the month your brain most needs the raw material is a reliable route to feeling worse and concluding you need to restrict further.
Habits for a smoother winter
Her four, unchanged, because they're the right four.
| Habit | What it actually is |
|---|---|
| Morning sunlight | Get outside for 5–10 minutes within an hour of waking |
| Don't skip breakfast | Eat a warm one. Temperature matters more than people expect. |
| Prioritise calm movement | Pilates, light weights, stretching, walking |
| Honour your cravings | Eat slowly, stop at 80% full |
Notice what isn't on the list: train harder, eat less, push through. Winter is not the season for a deficit, a new PB, or an aggressive protocol. It's the season for maintenance, and maintenance is not failure.
Where people go wrong
- Starting a restrictive plan on the first of January — the darkest, coldest, most cortisol-reactive month of the year. The worst possible timing, chosen annually.
- Reading the winter carb craving as weakness rather than as serotonin demand with a known mechanism.
- Getting morning light through a window. Glass filters out most of what you need. Outside, or it doesn't count.
- Extending the fasting window because motivation is low — which raises cortisol, which lowers motivation further.
- Comparing winter energy to summer energy and treating the gap as a problem to solve rather than a season to work with.
The one change
Get outside within an hour of waking, for five minutes, every day this week. No phone, no particular route, no need for sun.
It's the smallest intervention on this site and the one with the largest effect on everything downstream — cortisol, sleep, mood, appetite. Everything else in winter gets easier once the signal arrives on time.
Not sure which phase you're in this week? The Cycle Guide works it out for you — phase, fasting window, training and food.