What are macros? Protein, carbs and fat explained simply
"Macros" is short for macronutrients: the three nutrients your body needs in large amounts. They provide your calories.
The three macros
- Protein: 4 calories per gram. Builds and repairs muscle and other tissues, supports the immune system, and helps you feel full.
- Carbohydrate: 4 calories per gram. Your body's main fuel, especially for the brain and for exercise. Includes starchy foods, fruit, vegetables, and sugars.
- Fat: 9 calories per gram. Needed for hormones, absorbing some vitamins, and cell structure. It is the most calorie-dense.
Alcohol is not a macro, but it provides 7 calories per gram. Fibre, a type of carbohydrate your body mostly does not digest, is usually counted as about 2 calories per gram on UK labels.
Why track them at all?
Two meals can have the same calories and affect you very differently. A meal with plenty of protein and fibre usually keeps you fuller than one that is mostly refined carbohydrate. Tracking macros helps you see what is in your food and make choices that fit your goal.
Where do the numbers come from?
You can work out calories from grams:
- 30 g protein = 120 kcal
- 50 g carbohydrate = 200 kcal
- 20 g fat = 180 kcal
- Total = 500 kcal
Labels list protein, carbohydrate and fat per 100 g, and sometimes per portion.
Micronutrients are different
Vitamins and minerals are "micronutrients": needed in small amounts, and not counted as macros. A varied diet with plenty of vegetables, fruit and wholegrains usually covers them.
Where to start
Macro ratios explained
You will often see splits such as 40/30/30. These are the percentages of your calories from carbohydrate, protein and fat. To turn a ratio into grams, take the share of calories and divide by 4 (for protein and carbs) or 9 (for fat).
Example: 2,000 kcal at 40/30/30
- Carbs: 800 kcal ÷ 4 = 200 g
- Protein: 600 kcal ÷ 4 = 150 g
- Fat: 600 kcal ÷ 9 = about 67 g
Ratios are a handy shorthand, but they do not account for the size of the person. A fixed 30% protein is a lot for someone eating 1,400 kcal and little for someone eating 3,500. Many people find it more useful to set protein in grams per kilogram and fat as a share of calories, letting carbs fill the rest.
Common myths
- "Carbs make you fat." Eating more calories than you use makes you gain weight, whatever the source. Carbohydrate itself is not uniquely fattening.
- "Fat makes you fat." Fat is calorie-dense, so it is easy to overeat, but it is not special.
- "Protein is only for the gym." Everyone needs it, for muscle, bones, skin and the immune system.
- "All calories are equal in how they feel." The calories are equal, but protein and fibre keep most people fuller than refined carbohydrates.
Begin by knowing your calories, then see how your protein looks. Our guide to setting your macros shows how to turn it into daily targets. Foodie calculates and shows all three for every food you log. Try it free.