What are macronutrients

What are macronutrients?

Macronutrients or “macros” are the components of food that contribute to energy. Energy, in the nutritional sense, is measured in kilocalories (a.k.a. Calories) or kilojoules.

The main macronutrients are protein, fat and carbohydrates (a.k.a. “carbs” or “CHO” for the chemistry-minded people out there). Most foods you can think of are made of a combination or these 3 components.


Proteins are structures composed of amino acids. There are 7 essential amino acids for humans, meaning our bodies cannot make them. Foods high in protein include: all animal foods (meat, fish, poultry, eggs, milk, etc.), some legumes (beans, chickpeas, lentils, soy), and some nuts and seeds.

Protein bioavailability (i.e. how much of it we can actually absorb and utilise) varies depending on the source. In general, proteins of animal sources are more bioavailable than those from plant sources. Read my article on protein quality and quantity for more details.

Protein’s main role is not to provide energy. Instead, think of it as the main building block in the body. Again, read my article on protein quality and quantity for more details.


Fat still suffers from the stigma brought about with the low-fat diets that were all the rage decades ago. Fat is an important nutrient, essential for life. As with protein, there are essential fatty acids, important for cell structure and hormone production.

Fat is evidently present in foods of animal origin like meat, fish, poultry, butter and cheese. In addition, it is also present in fruits (avocados, olives, coffee, cacao, coconut), nuts, seeds and grains. Edible oils that are derived from fruits or seeds are mostly fat.


There are many ways to classify carbohydrates. One of those is sugars vs starches. Think of sugars as simple molecules and starches as networks.

Carbohydrates are mainly present in plant foods, such as fruits, vegetables, legumes and grains, plus the food made from those plants. Some nuts, like chestnuts and cashews are also high in carbohydrate. In general, fruits have more sugar, while grains and vegetables have more starch. Of course the amount of carbohydrates in different plants varies wildly. See the table below for some examples.

Energy in macronutrients

A long time ago scientists analysed the components of food to determine how much energy was given out when literally burning them. They found out that 1 gram of each macro produces the following amount of energy:

Macronutrient Energy (Cal) Energy (kJ)
Protein 4 17
Fat 9 37
Carbohydrate 4 17

Refer to the table below for energy, protein, fat and carbs in selected foods.

Other macronutrients


Although it is not normally considered a nutrient (in the “nutritious” sense), alcohol also contributes to energy intake. 1 gram of alcohol contributes 7 kilocalories or 29 kilojoules. To put this into context, a bottle of regular beer has 13.86 grams of alcohol, some carbohydrate and a tiny bit of protein, equating to 498.3 kilojoules. A 150ml glass of red wine contains 16.5 grams of alcohol and 486 kilojoules.


Ketones have also been put forward as an extra macronutrient, as they can be utilised as energy. However, ketones are most commonly endogenous, which means they are produced in the body. This happens, for instance, when fasting or eating a very low carbohydrate diet. You may also consume ketones in the form of exogenous (i.e. outside of the body) ketone salts, etc.

Macronutrient requirements

There are generic macronutrient range recommendations at a population level. However, individual recommendations vary based on body weight, age, gender, activity level, medical conditions, goals, etc.

If it fits your macros

There is an eating style popular among fitness enthusiasts called IIFYM (if it fits your macros), meaning you can eat whatever you want as long as the total amount of protein, carbs and fat match your calculated requirements for the day. More often than not, this turns into an excuse for eating junk food. Also, tracking food intake might not be a good idea long-term, as it might lead to obsessive behaviour and eating disorders.

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