Nutrition glossary
What is a macronutrient?
A macronutrient is a nutrient your body needs in large amounts, measured in grams, to supply energy and build and repair tissue. There are three: carbohydrate, protein and fat.
The three macronutrients
"Macro" means large. You eat these by the gram, compared with vitamins and minerals, which you need in milligrams or micrograms. Most foods contain a mix of all three, but usually one dominates.
- Carbohydrate is your body's main everyday fuel, and your brain's preferred one. It includes sugars, starches and fibre. You find it in bread, rice, pasta, potatoes, fruit, beans, milk and sweets.
- Protein builds and repairs muscle, skin, enzymes and hormones. It's in meat, fish, eggs, dairy, beans, lentils, tofu and nuts.
- Fat stores energy, helps you absorb vitamins A, D, E and K, and forms part of every cell. It's in oils, butter, nuts, seeds, avocado, oily fish and cheese.
Calories per gram
| Nutrient | Calories per gram | Example |
|---|---|---|
| Carbohydrate | 4 kcal | A 30 g slice of bread has about 15 g carbs, roughly 60 kcal from carbs |
| Protein | 4 kcal | A large egg has about 6 g protein, roughly 24 kcal from protein |
| Fat | 9 kcal | A tablespoon of olive oil has about 14 g fat, roughly 120 kcal |
| Alcohol (not a nutrient) | 7 kcal | Supplies energy but nothing your body needs |
This explains why fatty foods are so energy dense. A small handful of nuts can have as many calories as a large bowl of fruit.
How much of each do you need?
US guidance gives wide, flexible ranges for adults, as a share of daily calories:
- Carbohydrate: 45 to 65%
- Fat: 20 to 35%
- Protein: 10 to 35%
For protein, the basic recommendation for adults is 0.8 g per kilogram of body weight a day. A 70 kg (about 11 stone or 154 lb) adult would need about 56 g, which you could get from an egg at breakfast, a chicken breast at lunch and a bowl of lentils at dinner. Many people aim higher when losing weight or doing strength training, to help hold on to muscle.
The type of each macro matters as much as the amount. Whole grains, beans and fruit are better carbohydrate sources than sweets and white bread. Olive oil, nuts and oily fish are better fat sources than processed meats and pastries.
Macro ratios and diets
Many diets are really defined by their macronutrient ratio, the share of calories from each. A typical keto diet might be around 70% fat, 20% protein and 10% carbohydrate. A moderate low-carb diet might be 25 to 40% carbohydrate. The Mediterranean diet isn't defined by numbers at all, just by food choices.
Here's how a ratio turns into grams. On a 2,000 kcal day at 50% carbohydrate, 20% protein and 30% fat:
- Carbs: 1,000 kcal ÷ 4 = 250 g
- Protein: 400 kcal ÷ 4 = 100 g
- Fat: 600 kcal ÷ 9 = about 67 g
Weight loss studies generally find that when calories are matched, different macro ratios give fairly similar results. The ratio you can stick with tends to matter more than the ratio itself.
Macronutrients vs micronutrients
Micronutrients are the vitamins and minerals you need in tiny amounts, such as iron, vitamin C, calcium and the electrolytes. They don't provide calories, but you can't stay healthy without them. Fibre is technically a carbohydrate, and water is sometimes called a macronutrient too, since you need it in large amounts, even though it has no calories.
Common questions
What are the 3 main macronutrients?
Carbohydrate, protein and fat. Together they supply all the calories in your food, apart from alcohol.
Do I need to count macros to lose weight?
No. Counting macros can help some people, especially to make sure they eat enough protein, but you can lose weight by building balanced meals and eating a bit less overall. Weight loss comes from a calorie deficit.
Is fibre a macronutrient?
Fibre is a type of carbohydrate, so it falls under that macronutrient. Your body can't fully digest it, which is why low-carb dieters subtract it to get net carbs.
Related
For balanced meals without the maths, see healthy eating basics and diet quality. For carb-focused terms, read net carbs, glycemic index and added sugar. Comparing diets? Try diet comparisons and is there one best diet.