What Are Macros? The Complete Beginner's Guide to Macronutrients

TL;DR

• Macros (macronutrients) are protein, carbohydrates, fat and fibre, the building blocks of everything you eat
• Calories measure how much energy food gives you; macros tell you where that energy comes from
• Tracking macros is one of the most effective things you can do for weight loss or muscle gain
• Chowdown is a free AI macro tracker that logs your meals from photos in seconds

You’ve probably heard people say “I’m tracking my macros” and wondered what on earth they’re on about. It sounds complicated. Technical. Like something only bodybuilders and Instagram fitness influencers need to worry about.

It’s not. Macros are genuinely simple once you understand the basics, and tracking them is one of the most effective things you can do for your health, whether you want to lose fat, build muscle, or just feel better day to day.

Here’s everything you need to know, explained without the jargon.

What Are Macros, Exactly?

“Macros” is short for macronutrients: the three main types of nutrients your body needs in large quantities to function. Everything you eat is made up of some combination of these three:

• Protein — builds and repairs muscle, keeps you full
• Carbohydrates — your body’s primary energy source
• Fat — essential for hormones, brain function, and absorbing vitamins

There’s also fibre, which is technically a type of carbohydrate but important enough to track separately. Fibre supports digestion, gut health, and keeps you feeling full. Most people don’t get nearly enough of it.

Every food you eat contains some mix of protein, carbs, fat, and fibre. A chicken breast is mostly protein with a bit of fat. Rice is mostly carbs. An avocado is mostly fat with some carbs. A pizza? All three.

Calories vs Macros: What’s the Difference?

Calories measure how much energy food gives you. Macros tell you where that energy comes from.

Each macro contains a set number of calories per gram:

• Protein: 4 calories per gram
• Carbohydrates: 4 calories per gram
• Fat: 9 calories per gram

So if you eat 150g of protein, 200g of carbs, and 70g of fat in a day, that’s:

• 150 × 4 = 600 calories from protein
• 200 × 4 = 800 calories from carbs
• 70 × 9 = 630 calories from fat
• Total: 2,030 calories

This is why macro tracking is more useful than calorie counting alone. Two meals can have the same calories but completely different effects on your body depending on their macro split.

A 500-calorie meal of grilled chicken and vegetables (high protein, moderate carbs) will keep you full for hours and support muscle recovery. A 500-calorie meal of crisps and sweets (high carbs and fat, almost no protein) will leave you hungry again in 30 minutes.

Same calories. Very different outcomes.

Why Do Macros Matter?

For Weight Loss

If you want to lose fat, you need a calorie deficit. But how you fill those calories matters enormously.

Getting enough protein while in a deficit is critical. Protein preserves lean muscle mass, so you lose fat rather than muscle. It also keeps you fuller for longer, which means fewer cravings and less snacking.

Most people who “just count calories” without tracking macros end up under-eating protein. The result? They lose weight, but a chunk of that weight is muscle, not fat. Their metabolism slows down, they feel weak, and they regain the weight quickly.

For Muscle Building

Building muscle requires two things: resistance training and adequate protein. Most research suggests you need between 1.6g and 2.2g of protein per kilogram of body weight to maximise muscle growth.

Without tracking, most people massively overestimate how much protein they’re eating. You think that chicken wrap had 40g of protein? It probably had 20g.

For General Health

Even if you’re not trying to lose weight or build muscle, your macro balance affects:

• Energy levels throughout the day
• Sleep quality
• Mood and mental clarity
• Hormone function (fat is essential here)
• Digestive health (fibre is crucial here, and most people are deficient)
• Recovery from exercise

Getting the right balance for your body makes a noticeable difference in how you feel every day.

What Should Your Macros Be?

There’s no single answer that works for everyone. Your ideal macro split depends on your goals, body weight, activity level, and preferences. But here’s a solid starting point:

For Fat Loss

• Protein: 2g per kg of body weight
• Fat: 0.8–1g per kg of body weight
• Carbs: fill the remaining calories

For a 75kg person aiming for 1,800 calories per day:

• Protein: 150g (600 cal)
• Fat: 65g (585 cal)
• Carbs: 154g (615 cal)

For Muscle Gain

• Protein: 1.8–2.2g per kg of body weight
• Fat: 0.8–1.2g per kg of body weight
• Carbs: as high as your calorie target allows (carbs fuel training)

For Maintenance

• Protein: 1.6–2g per kg of body weight
• Fat: 1g per kg of body weight
• Carbs: fill the rest

The one constant across all goals: protein stays high. It’s the most important macro to track. And don’t forget fibre: aim for at least 25-30g per day regardless of your other goals. Most Western diets fall well short of this.

If you do nothing else, just hitting your protein and fibre targets will make a meaningful difference.

You can quickly calculate your personal targets with a free macro calculator that accounts for your weight, height, age, activity level, and goals.

How to Start Tracking Macros

Step 1: Calculate Your Targets

Use a macro calculator to get your daily protein, carb, and fat targets. Chowdown’s free calculator does this in about 30 seconds.

Step 2: Track What You Eat

Log your meals using a nutrition tracking app. The old-school method is searching a food database and manually entering everything, but that’s tedious and most people give up within a week.

The modern approach? AI food scanning. Point your phone camera at your plate, and the AI identifies the food and estimates the macros for you. It’s not perfect, but it’s fast enough to actually stick with.

Step 3: Focus on Protein First

Don’t try to hit all three macros perfectly from day one. That’s overwhelming. Instead:

1. Week 1: Just track everything without changing your diet. See where you’re starting from.
2. Week 2: Focus on hitting your protein target. This usually means adding a protein source to each meal.
3. Week 3+: Start adjusting carbs and fats to match your targets.

Most people are shocked by their Week 1 numbers. “I thought I was eating loads of protein” is the most common reaction, usually followed by discovering they were eating half of what they need.

Step 4: Keep It Simple

You don’t need to weigh every gram of food. Eyeballing portions and scanning meals with AI gets you close enough for meaningful results. Perfectionism kills consistency, and consistency is what actually matters.

Track for a few weeks and you’ll start to develop an intuition for what’s in your food. Eventually, you’ll be able to estimate macros without logging every single thing.

Common Macro Tracking Mistakes

Mistake 1: Obsessing Over Exact Numbers

Hitting 148g of protein instead of 150g is not a failure. Aim for within 10% of your targets and you’re golden. Nutrition is not a precise science, and your body doesn’t care about single-gram accuracy.

Mistake 2: Ignoring Fat

Some people try to eat as little fat as possible, thinking fat makes you fat. It doesn’t. Dietary fat is essential for hormone production, vitamin absorption, and brain function. Cutting it too low will make you feel terrible.

Mistake 3: Cutting Carbs Unnecessarily

Carbs are not the enemy. They’re your body’s preferred energy source, especially for exercise. Unless you have a specific medical reason to restrict carbs, there’s no need to go low-carb. Just make sure you’re getting enough protein and healthy fats first.

Mistake 4: Not Tracking Drinks

That latte has 150 calories and 12g of sugar. That “healthy” smoothie might have 60g of carbs. Drinks add up fast and are easy to forget. Track them.

Mistake 5: Giving Up After a Bad Day

Everyone has days where they eat way off-target. Birthday parties, takeaways, holidays. It doesn’t matter. One day changes nothing. What matters is the average over the week and month.

Do You Need to Track Macros Forever?

No. Think of macro tracking as a learning tool, not a life sentence.

Most people benefit from tracking seriously for 3 to 6 months. During that time, you build an understanding of what’s in your food, what portions look like, and what a balanced day of eating feels like.

After that, many people can maintain their results with loose tracking or intuitive eating, checking in with proper tracking every now and then to recalibrate.

The goal isn’t to become obsessed with numbers. It’s to make informed choices about what you eat.

Start Tracking for Free

Most macro tracking apps charge £5 to £15 per month for features that should be free, and many don’t even track fibre. Chowdown gives you everything you need at no cost: AI food scanning, full macro tracking including fibre, personalised targets, and meal insights. No premium tier, no paywall, no “free trial” that expires.

Try the free macro calculator →

Your macros aren’t a mystery. Once you see the numbers, everything clicks.