When the Light Goes Out: A Lifestyle Medicine Approach to Depression

It was Mr DH’s wife who made the appointment.

For months she had watched her husband slowly disappear. He was 58 and worked in corporate sales. He used to be the life of the party, the friend who never said no to a night out and the dad who could make anyone laugh. Now he came home, sat in front of the TV and fell asleep there. He barely spoke to the children. When friends phoned, he found an excuse.

When he sat down across from me, he smiled politely, but the smile never reached his eyes.

“Doc, it feels like my battery has been completely drained.”

I’ve sat with thousands of patients over the years. There is a clinical checklist for depression, but often you don’t need it, because you can feel it. The light has gone dim, and sitting with that person, you feel a little heavier yourself.

So let’s talk about what depression really is, why it’s about far more than “brain chemicals”, and the everyday changes that helped Mr DH find his way back to himself.

First things first: depression is real

Depression is not weakness, laziness or something you can simply “snap out of”. It is a real medical condition that affects the brain and body, and it can be serious. When people feel this unwell, relationships can suffer, careers can derail and, sadly, some people come to feel that life isn’t worth living.

So I’ll say this clearly: if your depression is severe, lifestyle changes on their own are not enough. Medication and more intensive medical care may be needed, and there is no shame in that. Very often the best results come from combining medication with the kind of lifestyle support I’m about to describe.

It’s not just “low serotonin”

You may have heard that depression is caused by a lack of serotonin, the brain’s “feel-good” chemical. That was the thinking for many years, but we now know the picture is much more complicated.

Depression doesn’t look the same in everyone. Some people mainly feel flat and empty, and things that used to bring joy just don’t anymore. Others feel wired, irritable and unable to sleep. Many feel anxious as well as low.

Several brain messengers are involved: serotonin, dopamine, noradrenaline and adrenaline. So is the way brain cells communicate with each other, and so are systems well beyond the brain, in the gut, the immune system and the body’s stress response. That’s good news, because those are exactly the areas where your daily habits can make a real difference.

Is it depression, or am I just going through a hard time?

We all have low days. Depression is different. It’s a low mood that stays and colours everything, together with a loss of pleasure, low energy and withdrawal from life, lasting more than about two weeks.

When I’m deciding how to help a patient, I ask three simple questions. You might find it useful to ask yourself the same ones.

How long has this been going on? If it has been weeks or months rather than days, it’s time to talk to someone.

How is it affecting your everyday life? Patients often tell me things like, “I can’t get out of bed. I’ve stopped going to work. My husband has to pack the kids’ lunches because I just can’t.” When depression starts taking away your ability to show up for your work, your family or the things that matter to you, it needs attention.

Have you had any dark thoughts? If you’ve had any thoughts of harming yourself, or feel that the people around you would be better off without you, please reach out for help today, not tomorrow. Speak to your doctor, a crisis line or your local emergency services. You’ll find support contacts at the end of this article.

What’s happening behind the scenes?

Depression rarely appears out of nowhere. In almost every patient I see, there’s a story of long-term stress underneath it: pressure at work, family strain, grief or a major life upheaval. That long-term stress affects the body in three important ways.

It fuels inflammation. Constant stress keeps the body in a low-level “on alert” state, a kind of quiet, simmering inflammation. Many people with depression carry more of this inflammation, and it weighs on the brain.

It unsettles the gut. Your gut and brain are in constant conversation. The trillions of bacteria living in your gut help produce and balance the chemical messengers that affect your mood. When the gut is out of balance, the brain feels it.

It wears down the immune system. When your stress glands pump out cortisol month after month, your immune system is thrown off balance. Because the immune and nervous systems are so closely linked, your mood suffers too.

The encouraging part is that all three respond to how you live, day by day.

Five everyday habits that can help lift mood

1. Move, even just a little

This one surprises people, but movement is one of the most powerful mood-lifters we have. Walking, jogging, dancing, yoga, strength training and tai chi can all help, and the more you’re able to do over time, the bigger the benefit tends to be.

The trick is to start where you are. If getting off the couch feels impossible right now, that’s okay.

Try this: Take a 10-minute walk, two or three times this week. That’s all. Once it feels doable, add a few minutes or an extra day.

2. Refill your nutrient tank

Months of stress burn through nutrients faster than usual. On top of that, depression often steals your appetite, so many people end up quietly undernourished without realising it. The nutrients I most often find running low are vitamin B12 and the other B vitamins, vitamin D, magnesium, iron and protein, all of which your brain needs to make its mood messengers.

What’s on your plate matters too. People who move towards simple, whole foods, like vegetables, fruit, nuts, seeds, good-quality protein and healthy fats, and away from sugar and ultra-processed foods, often notice a real difference in how they feel.

Try this: Ask your doctor about a simple blood test to check your B12, vitamin D and iron. And swap one packaged snack a day for real food: an egg, a handful of nuts or a piece of fruit.

3. Give your day an anchor

Your brain loves rhythm. Getting up and going to bed at roughly the same time every day helps settle your brain chemistry into a healthy pattern. Good sleep also gives your brain a chance to do its nightly “clean-up”, clearing out the waste that builds up during the day.

When you’re feeling low, it’s very tempting to stay in bed. But lying in bed all day tends to make things worse, not better. Getting up and into daylight is one of the kindest things you can do for your mood.

Morning light is especially powerful. When natural light reaches your eyes early in the day, it resets your internal body clock, which helps set your energy, sleep and mood for the next 24 hours.

Try this: Get up at the same time every day, weekends included, and spend 10 to 15 minutes outside within an hour of waking. Take your coffee onto the balcony, or go for a short walk.

4. Let someone in

Depression pulls you inward. Being around people feels exhausting, and things you used to enjoy with friends feel flat. But withdrawing leaves more time alone to go over and over how bad you feel, and loneliness deepens the low.

You don’t need a crowd. You need one person: someone warm and non-judgemental who won’t lecture you or try to “fix” you, and who will simply be there.

Try this: Think of one person who makes you feel safe, and plan a short coffee or a walk together this week.

5. Talk it through with a professional

A psychologist or counsellor offers something that even the most loving family member can’t: an outside perspective and a safe, private space to unpack what’s going on. Many people find their depression has roots in grief, burnout or stress they’ve never had the chance to process, and working through that can be a turning point.

Try this: Ask your doctor for a referral to a psychologist or counsellor.

Mr DH’s story: slow, steady and remarkable

When I started asking Mr DH about his life, the story came out. His father had recently died of cancer, and Mr DH had been his caregiver through those final months. At the same time, work was relentless. He had never had a moment to grieve.

He was exhausted but sleeping too much. He’d lost his sense of humour and his appetite, and had dropped 5 kg in three months. He couldn’t concentrate at work, had missed several days and was falling behind on his targets. He was getting through the day on coffee, muffins and energy drinks, and unwinding with beer in the evenings.

He assured me he wasn’t having any thoughts of harming himself. He was also very clear that he didn’t want antidepressants. His sister had had a frightening reaction to one, and he was scared.

So we made an agreement. We would try lifestyle medicine first, on the condition that he checked in with me every week, had my number to call if things ever felt darker, and started seeing a psychologist to help him grieve for his father.

Here’s what we did:

• His blood tests showed low vitamin B12, vitamin D and magnesium, so we topped those up.
• With his wife sitting beside him, he agreed to get up each morning and go for a walk in nature in the early sunlight.
• He kept his coffee to one cup a day, in the morning.
• He swapped the muffins, energy drinks and beer for real, nourishing food: no sugar or refined starches, with plenty of protein, healthy fats, vegetables, fruit, nuts and seeds.

Then we waited.

After about three weeks, I noticed it first in his face. When he smiled, he meant it. There was a little more energy and enthusiasm, and a glimmer was coming back into his eyes.

At six weeks, he told me his energy was definitely improving, and that he had actually started looking forward to his morning walks with his wife.

By three months, he was back at work at full capacity, managing everything he used to and performing at his normal level again.

His recovery wasn’t quick, and it wasn’t one single thing. It took time, several changes working together, and a lot of support. But it worked, and not one of those changes came with a side effect.

So, medication or lifestyle?

For many people, the answer is both. Antidepressants help a great many people and can be lifesaving, especially when depression is severe. I never want anyone to feel they’ve “failed” because they need medication.

What I do want you to know is that you have more influence over your brain health than you might think. The way you eat, move, sleep and connect gives your brain the raw materials and conditions it needs to heal, whether or not you also take medication.

Depression is very common, and it is very treatable. Be as gentle with yourself as you would be with someone you love, and if someone close to you is struggling, meet them with patience and kindness. With the right support, many people come through depression stronger and wiser than before.

Watch the full session

[YouTube embed: “Depression: Mechanisms and Management | Dr Karen Hartzenberg”]

Go deeper with Brain Food for Vitality

This article comes from the Mental Health Series in Brain Food for Vitality, our course on how what you eat shapes how you think, feel and function. It’s full of real patient stories and practical tools, with sessions on anxiety, burnout, sleep and more.

👉 Enrol in Brain Food for Vitality Here
📋 Not sure where to start? Download the free Brain-Health Risk Checklist here

Brain Food for Vitality was created by Dr Karen Hartzenberg, Dr Micki Pistorius (Neuropsychologist) and Yovanee Veerapen (Registered Dietitian, NutriSmart).

Need support right now?

If you’re having thoughts of suicide or self-harm, please reach out today. Contact your doctor, your local emergency number or a crisis helpline in your country. You can find a free, confidential helpline near you at findahelpline.com.

In Mauritius: Befrienders Mauritius 800 9393 (daily, 09:00–21:00) · SAMU 114 (emergencies)

This article is for educational purposes and does not replace personalised medical advice. Please don’t stop or change any prescribed medication without speaking to your doctor. Patient details have been anonymised.

Further reading

• Moncrieff J, et al. The serotonin theory of depression: a systematic umbrella review of the evidence. Molecular Psychiatry, 2022.
• Osimo EF, et al. Prevalence of low-grade inflammation in depression: a systematic review and meta-analysis of CRP levels. Psychological Medicine, 2019.
• Noetel M, et al. Effect of exercise for depression: systematic review and network meta-analysis of randomised controlled trials. BMJ, 2024.
• Jacka FN, et al. A randomised controlled trial of dietary improvement for adults with major depression (the “SMILES” trial). BMC Medicine, 2017.
• Firth J, et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosomatic Medicine, 2019.
• Burns AC, et al. Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people. Nature Mental Health, 2023.
• Santini ZI, et al. Social disconnection, perceived isolation, and symptoms of depression and anxiety among older Americans. Lancet Public Health, 2020.