What exactly are macronutrients?

Macronutrients are the three main groups of nutrients your body needs in large amounts: carbohydrates, proteins and fats. Between them, they supply the energy that keeps your heart beating, your brain thinking and your muscles moving. Unlike vitamins and minerals — the micronutrients — you need macronutrients in grams rather than milligrams, which is why they take up most of the space on your plate.

Each one has its own job. Carbohydrates are the quickest source of fuel, protein provides the building blocks for repair, and fats support everything from hormone production to absorbing certain vitamins. None of them is the villain of the story, and none of them works well in isolation. The aim isn't a perfect ratio — it's a steady, varied supply that keeps your body and your gut comfortable.

Carbohydrates: your body's preferred fuel

When you eat bread, oats, potatoes, rice, fruit or yoghurt, your body breaks the carbohydrate down into glucose, which fuels your muscles and is the preferred energy source for your brain. That's why cutting carbs dramatically can leave you foggy and flat.

Not all carbohydrates behave the same way, though. Fibre is a type of carbohydrate you can't fully digest, and it's one of the most valuable things you can eat for gut health. It feeds the bacteria in your large intestine, helps keep you regular and slows the release of glucose into the bloodstream.

• Base meals on starchy foods: wholemeal bread, oats, brown rice, wholewheat pasta or potatoes with the skin on.
• Aim for around 30g of fibre a day — most adults in the UK manage closer to 18g.
• Build up fibre gradually and drink plenty of water, or you may feel bloated at first.
• Keep sugary drinks and sweets as occasional extras rather than everyday fuel.

Protein: repair, rebuild, recover

Protein is made up of amino acids, nine of which your body can't make itself. They're essential for repairing muscle after exercise, supporting your immune system, making enzymes and keeping skin, hair and nails in good shape.

Most adults need roughly 0.75g of protein per kilogram of body weight per day, and more if you're active, over 65, pregnant or recovering from illness. The trick many people miss is spreading it across the day rather than loading it all into one evening meal.

• Two eggs at breakfast gives you around 12g of protein.
• A 150g pot of Greek yoghurt adds roughly 15g.
• A small tin of tuna, a chicken breast or a salmon fillet provides 25–30g.
• Lentils, chickpeas, beans, tofu and nuts count too — pair pulses with grains such as rice or bread for a fuller range of amino acids.

Fats: small amounts, big jobs

Fat has a reputation it doesn't deserve. It insulates your organs, helps make hormones, forms part of every cell membrane and allows you to absorb vitamins A, D, E and K. It also makes food taste good and helps you feel satisfied after a meal.

The type of fat matters more than the total. Unsaturated fats — olive and rapeseed oil, nuts, seeds, avocado and oily fish — are the ones to favour. Saturated fats found in butter, cheese, fatty meat and pastries are fine in moderation, but it's worth keeping them in the minority.

• Use a thumb-sized portion of oil, butter or nut butter per meal as a rough guide.
• Try to eat one portion of oily fish, such as salmon, mackerel or sardines, each week.
• A small handful of unsalted nuts or seeds makes an easy, satisfying snack.

Building balanced meals without counting every gram

You don't need an app or a set of scales to eat well. A simple visual guide works surprisingly well: a palm-sized portion of protein, a cupped-hand portion of carbohydrates, a thumb of fat and at least a fistful of vegetables or salad. Adjust the amounts to your appetite, activity level and goals.

Regular meals help too. If you skip breakfast and then graze all afternoon, you're more likely to reach for quick sugary options and less likely to hit your fibre and protein targets. A little planning — batch-cooking a lentil curry, keeping eggs and yoghurt in the fridge, chopping vegetables on a Sunday — makes balanced eating far easier on a busy Tuesday.

Macronutrients, gut comfort and food sensitivity

Your gut bacteria thrive on variety. Aim for around 30 different plant foods a week — vegetables, fruit, wholegrains, nuts, seeds, herbs and spices all count. Fermented foods such as live yoghurt, kefir, sauerkraut and miso can support a diverse microbiome as well.

If certain foods leave you bloated, windy or rushing to the loo, it's worth paying attention rather than pushing through. Sensitivities often relate to specific components — lactose in milk, FODMAPs in onion, garlic and wheat, or histamine in aged cheeses and cured meats — rather than to a whole macronutrient group. Cutting out carbohydrates or fats entirely is rarely the answer and can leave gaps in your nutrition.

Instead, keep a simple food and symptom diary for a fortnight, noting portion sizes as well as foods, since reactions are often dose-related. Eat slowly, chew properly and give your gut a chance to settle. If symptoms persist, speak to your GP or a registered dietitian before making big changes — they can help you pinpoint the trigger while keeping your diet balanced and enjoyable.