Diet Principles #3: Macronutrients

Following on from Diet Principles #2: Metabolic Adaptation we are now going to look at macronutrients. Macronutrients are a very important factor when it comes to nutrition. Although calories in vs calories out is the fundamental principle to losing/maintaining/gaining weight, macronutrients come into play to aid in muscle growth, feeling fuller for longer and many other health benefits.

What are macronutrients?

So what are macronutrients? Macronutrients are nutrients that are required in large quantities. These nutrients are needed for growth, energy provision and other body functions. They are essential to carry out the activities of daily life. There are 3 macronutrients – these are carbohydrates, proteins and fats.

You may have heard of If It Fits Your Macros (IIFYM) and this is essentially eating foods that meet a predetermined amount that has been set for each of these macronutrients. This has become a very popular ‘dieting’ trend which is actually very good and does not restrict types of food. A full article will be posted in the near future looking deeper into IIFYM.

Macronutrients give our bodies energy. The amount of energy supplied varies between each of these three macronutrients – Carbohydrates and proteins each provide 17kJ per gram whereas fats provide 37kJ per gram. This translates to about 4kcals per gram and 9kcals per gram respectively. We would typically look at these measurements using the kcals unit as this makes it easier for tracking.

When on a nutrition plan the intake of each of these macronutrients is often split into percentages. Just what percentages these are vary depending on goals. An example of this coule be of an active teenager who is burning 2500kcals of energy per day and therefor needs to eat atleast this amount to maintain bodyweight. With no other goal than to maintain bodyweight his macronutrients could be split into 55% carbohydrates, 30% fats and 15% protein. This would leave our active teenager eating around 344g of carbohydrates, 83g of fats and 94g of protein.

As mentioned before the percentages vary depending on ones goals. A bodybuilder for example will require a much larger protein intake to aid in muscle recovery and therefore carbohydrates or fats usually then have to take a fall.

Why do we need carbohydrates?

Carbohydrates are typically required in the largest amounts. Whean eaten and broken down within our bodies, carbohydrates provide the major source of energy to help fuel our daily lives. Some carbohydrates that we consume are stored as glycogen within our livers and muscles as a kind of reserve for our bodies to use later if needed.

Why do we need proteins?

Proteins consumed in our daily diets are broken down into what’s known as amino acids. The body then uses these amino acids in a few different ways. One way it uses these amino acids is to grow and repair tissue (hence why we need to eat more when weight training and trying to increase muscle size). These amino acids can also be used as an energy source. Finally they can be used as starting materials for the production of other compounds needed by the body.

All proteins within the body are made up of up to 20 different amino acids. 8 of which are often described as ‘essential’ amino acids which means that the food we eat must contain proteins capable of supplying these. The others can be synthesised by the liver if not included in our diets. Protein that is drawn from animal sources within our diets contain all the essential amino acids. Plant sourced proteins however do not. By eating a variety of plant sources, the amino acids can be supplied, however.

Why do we need fats?

Fats. Negative connotations are probably already gathering in your head when you hear the word. Despite the false bad reputation of fats, they are essential for health and wellbeing. In addition to supplying energy fats also supply fatty acids that the body is unable to produce on its own (omega-3 for example), assist with absorption of the fat-soluble vitamins A, D, E and K and carotenoids and also provides food with that delicious flavour and texture.

There are 3 main types of dietary fats; saturated, unsaturated and trans. Saturated fats are found in foods such as meat, butter and cream (animal sources). Unsaturated fats are found in the likes of olive oil, avocados, nuts etc (plant based sources). Trans are typically found within comercially produced baked goods, snack foods, fast foods and some margarines.

Fats are not as bad as they seem, but the wrong types in copious amounts has been shown to lead to heart disease. It is typically said that replacing saturated and trans fats with unsaturated fats can help decrease the risk of heart disease.

It is recommended that 20-35% of our daily energy intakes should be made up of fats. This again is for the average person and varies dependant on your individual goals. Fats should definitely not be neglected from your nutrition.


I hope this article has helped to de-mystify macronutrients for you and help you in achieving your goals. We have broken down the 3 macronutrients and had a look at why each are important in our daily diets. Again as mentioned throughout, the macronutrient ratio is entirey dependent on goals and even each individual. For example when it comes to weight loss – some people actually react better to a higher fat, lower carbohydrate ratio and vice versa. This is where experimentation needs to take place and just overall getting to know your body and what works best for it.

In the next Diet Principles article we will be taking a look at Micronutrients. Keep an eye on our social media platforms for updates!

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