Macronutrients — protein, carbohydrate, and fat — are the three categories that dietary energy comes from. Every food that contains calories contains some combination of the three. Understanding what each one does in the body, without assigning hierarchy or treating any as a villain, is the most useful foundation for nutrition literacy.
Protein
Protein is the structural macronutrient. It provides the raw material for muscle tissue, enzymes, hormones, immune system components, and most of the body's functional machinery. It is made of amino acids, nine of which are essential — the body cannot synthesise them and must obtain them from food.
When you eat protein, it's broken down into amino acids in the digestive tract and reassembled into whatever the body needs. In the context of training, the most relevant use is muscle protein synthesis — the process by which damaged or depleted muscle tissue is rebuilt and, with the right stimulus, built back slightly larger and stronger.
Protein also has a higher thermic effect than other macronutrients, meaning more energy is spent processing it. It is also the most satiating macronutrient per calorie — something covered in more detail in the article on satiety.
Carbohydrate
Carbohydrate is the body's preferred energy currency. It is broken down into glucose, which circulates in the blood and is used by cells for immediate energy, or stored as glycogen in the muscles and liver for later use.
The brain runs almost exclusively on glucose. Skeletal muscle uses glucose heavily during high-intensity exercise. Glycogen stores are finite — roughly 400–500g total — which is why carbohydrate intake around training is relevant: depleted glycogen limits performance, and replenishing it after training supports recovery.
Dietary fibre — which is technically a form of carbohydrate — is not digested for energy but performs important roles in gut health, blood glucose regulation, and satiety. It is covered in detail in the article on fibre and food quality.
Fat
Fat is the body's primary long-term energy storage mechanism and a critical structural component. Cell membranes are made of phospholipids — fat molecules. Fat-soluble vitamins (A, D, E, K) require dietary fat to be absorbed. Hormones, including sex hormones and cortisol, are synthesised from cholesterol, a type of fat.
Fat is the most energy-dense macronutrient at approximately 37 kJ per gram, compared to 17 kJ per gram for both protein and carbohydrate. This density is often used to argue that fat is responsible for overconsumption — the argument doesn't hold up well across populations, but it does mean that dietary fat contributes to energy intake more per gram than the other two macronutrients.
Different fats have different physiological properties. Unsaturated fats (from sources like olive oil, avocado, nuts, and fatty fish) support cardiovascular health. Saturated fats (from animal sources primarily) have a more complex relationship with cardiovascular health that the evidence continues to refine. Trans fats — largely removed from the food supply in Australia — have clear negative health associations.
None of these are optional
This is worth stating plainly: the body requires all three macronutrients to function well. Approaches that eliminate or severely restrict any one macronutrient for extended periods create deficits in its functions. Low-carbohydrate approaches work for many people by other mechanisms (primarily satiety and reduced caloric intake), not by making carbohydrate redundant. Low-fat approaches similarly. The macronutrient itself is not the problem or the solution in any of these contexts.
Intentra tracks all three because all three matter. The balance between them is something to adjust based on your goals and what evidence suggests is useful — not based on which one has the worst reputation this year.