Macronutrients | Their Roles In The Body

Written by Jamie Bantleman

Macronutrients and Their Roles in the Body

Protein, Fats and Carbohydrates make up the three macronutrients that we fuel our bodies with at different points in the day for different reasons. There are many different opinions and ideas of what the nutrients are best for and if and when to use them; these are often quite misleading and because it works for one person doesn’t necessarily mean it will work for everyone therefore it is important that we stick to the facts.


We were told for years that fat was bad for us, now we are told that carbs are bad for us, and that meat is full of ‘toxins’ and that it may be healthier to be vegan but then others say being vegan is massively unhealthy and that the blood profiling of a vegan is much worse than that of a meat eater. Confused? Try listening to these on-going debates every single day and making an educated conclusion for what suits you and/or clients if you are personal trainer!!


The only way to ensure you are making the right decisions is looking deep into the facts of what the different nutrients actually offer you and your body both physically and hormonally. Firstly, we will start with Protein, a macro that is broken down simply into essential amino acids. There are 500 known amino acids, 21 of which are needed by humans. Of the 21 necessary for life, nine are considered essential since they cannot be produced by the body and must be eaten.


Proteins that contain all nine essential amino acids are considered ‘high quality’ proteins. These high quality proteins tend to come from animal sources. Proteins that do not contain all nine essential amino acids are considered ‘low quality’ proteins, and tend to come from plant sources. Proteins are used to produce new tissues for growth and tissue repair, and regulate and maintain body functions.


Enzymes used for digestion, protection, and immunity are made of protein, and essential hormones used for body regulation require protein. Finally, proteins may be used as a source of energy when carbohydrates are not available. Protein is found in meats, poultry, fish, meat substitutes, cheese, milk, nuts, legumes, and in smaller quantities in starchy foods and vegetables.

cheesy stuffed meatballs low carb high fat snacks

Secondly, Carbohydrates are a macro that is a necessity for different reasons and as you can see from the following content, the proof is in the pudding – or the broccoli! When we talk about carbohydrates we usually relate this with the likes of pasta, potatoes, rice and foods that are processed. Invariably, we are looking for improved body composition and these foods are known for not exactly helping our cause; for this reason people take out carbohydrates completely.


However, fibre is a part of the carbohydrate macronutrient. Fibre is an indigestible form of carbohydrate. Since humans cannot break down fibre carbohydrates, they pass through the digestive system whole and take other waste products with them. Diets low in fibre have problems with waste elimination, constipation, and haemorrhoids. Diets high in fibre have shown decreased risk for obesity and high cholesterol. Fruits, vegetables, and whole grain products all contain high amounts of fibre.


Carbs are broken down into its simplest form into sugar and therefore glucose is then used as an energy source.

carb back loading

Finally, Fats. Fats are broken down into essential fatty acids. Fat also helps you absorb vitamins A, D, E, and K, the so-called fat-soluble vitamins. Fat also fills your fat cells and insulates your body to help keep you warm. The fats your body gets from your food give your body essential fatty acids called linoleic and linolenic acid. They are called “essential” because your body cannot make them itself, or work without them. Your body needs them for brain development, controlling inflammation, and blood clotting.


From looking at the above, I take the opinion of all of these macronutrients are vital and a necessity in the diet. The human body utilises all of these major nutrients and it is important to make sure we have a balance between all three when we are planning a diet.

Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

Claire Muszalski

Claire Muszalski

Registered Dietitian

Claire is a Registered Dietitian through the Academy of Nutrition and Dietetics and a board-certified Health and Wellness Coach through the International Consortium for Health and Wellness Coaching. She has a Bachelor of Science in Biology and a Master’s degree in Clinical Dietetics and Nutrition from the University of Pittsburgh.

Talking and writing about food and fitness is at the heart of Claire’s ethos as she loves to use her experience to help others meet their health and wellness goals.

Claire is also a certified indoor cycling instructor and loves the mental and physical boost she gets from regular runs and yoga classes. When she’s not keeping fit herself, she’s cheering on her hometown’s sports teams in Pittsburgh, or cooking for her family in the kitchen.

Find out more about Claire’s experience here.

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