How to Beat the Autumn Energy Slump (It's Not What You Think)

The weather cools. The days get shorter. And somewhere around late March or April, a significant number of my clients message me with a version of the same thing.

“I just feel flat. I’m sleeping but I wake up tired. I can’t seem to get going. Is something wrong with me?”

Nothing is wrong with them. What they're experiencing is the autumn energy slump and it's real, physiological and it has very specific causes that we can actually address with nutrition and a few lifestyle tweaks.

Let me explain what's actually happening.

Why autumn makes you tired

1. Your vitamin D drops — fast

Vitamin D is made in your skin from direct sunlight. In summer, most Australians get adequate sun exposure without even trying. But as autumn arrives, the sun sits lower in the sky, daylight hours shorten, and we spend more time inside. Within a matter of weeks, vitamin D production slows significantly.

This matters more than most people realise. Vitamin D is technically a hormone, not just a vitamin. It's involved in immune function, mood regulation, calcium absorption and critically for energy and thyroid support. Low vitamin D levels are strongly associated with fatigue, low mood, and general flatness. And up to 75 per cent of Australians are estimated to be vitamin D deficient even before the days start shortening.

If you haven't had your vitamin D checked recently, autumn is exactly the right time to do it.

2. Your circadian rhythm shifts

Your body's internal clock is set by light. Specifically, morning light hitting your eyes triggers a cascade of hormonal events — cortisol rises to wake you up, serotonin production kicks in, and the stage is set for melatonin to rise appropriately at night.

When daylight hours shorten, this process is compressed. You may be waking up before the sun, driving to work in darkness, spending all day inside under artificial light, and driving home in darkness again. Your circadian rhythm becomes confused. Cortisol patterns shift. Serotonin drops. And you feel perpetually tired regardless of how many hours you sleep.

This isn't a willpower problem. It's a light problem.

3. Your eating patterns drift toward comfort foods

Cooler weather activates our instinct to eat more carbohydrate-heavy, warming foods — and there's actually some evolutionary logic to this. But the specific foods most people reach for in autumn (pasta, bread, biscuits, processed cereals) spike blood sugar and then drop it hard, creating the fatigue-craving cycle that drags energy down across the whole day.

Autumn is not the time to give up nourishing food. It's actually the time to lean into it more deliberately.

What to do about it

Get your vitamin D levels tested

Ask your GP for a blood test. If you're below 75 nmol/L, supplementation is worth discussing. Look for a vitamin D3 combined with vitamin K2 — the K2 helps direct the calcium where it needs to go. Food sources include grass-fed butter, ghee, egg yolk, salmon, mackerel and sardines. Sun exposure in the morning (not midday) for 15–20 minutes on arms and face is still the most efficient source.

Prioritise morning light

Even on cloudy days, outdoor morning light is significantly brighter than indoor artificial light. A 15-minute walk outside in the morning — before you reach for your phone or sit at your desk — can meaningfully shift your cortisol rhythm and serotonin production for the entire day. This is one of the simplest and most evidence-backed habits I recommend, and it costs nothing.

Eat for energy, not just warmth

The autumn kitchen is actually rich with nourishing options. This is the season for slow-cooked proteins (chicken soups, lamb stews, bone broth), root vegetables (sweet potato, pumpkin, beetroot), and warming spices (turmeric, ginger, cinnamon) that support blood sugar stability and reduce inflammation.

The key is anchoring every meal with protein and fat before adding carbohydrates. A bowl of pasta for dinner will drop your energy. A lamb stew with vegetables and a small amount of potato will sustain it.

Lean into magnesium

Magnesium is involved in over 300 bodily functions including energy production, muscle relaxation, sleep quality and stress regulation. Deficiency is associated with fatigue, poor sleep and low mood — the exact symptoms of the autumn slump. And because stress depletes magnesium, and most of us are carrying some level of chronic low-grade stress, deficiency is extraordinarily common.

Food sources include dark leafy greens, pumpkin seeds, almonds, avocado, dark chocolate (there it is again), and black beans. An Epsom salt bath in the evening for just 20 minutes is also a surprisingly effective way to absorb magnesium through your skin.

Support your serotonin

Serotonin which is your mood and wellbeing hormone, is produced in the gut and in the brain, and its production requires tryptophan (an amino acid found in protein-rich foods), B vitamins, and a healthy gut microbiome. Ninety per cent of your serotonin is made in your gut. This is why what you eat directly affects how you feel.

Foods that support serotonin production include turkey, chicken, eggs, salmon, nuts and seeds, and fermented foods like kefir and kimchi. The connection between gut health and mood is one of the most exciting areas of nutrition science — and the practical takeaway is simple: feed your gut well, especially in winter.

A note on always feeling tired

If fatigue is persistent and if you're tired regardless of season, regardless of how much you sleep or regardless of what you eat, it's worth looking deeper. Thyroid dysfunction, iron deficiency, vitamin B12 deficiency, and hormone imbalances (particularly cortisol and oestrogen patterns) are common and commonly missed.

A simple blood panel with your GP covering these markers is a worthwhile investment. Don't accept 'you're just busy' or 'it's normal for your age' as an answer if you know in your gut that something is off.

Yours in good health and some dark chocolate. 🍫

Michele