Macronutrients and their role in human health

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Key points

  • Proteins, fats, and carbohydrates are the three main macronutrients in the human diet
  • All three macronutrients provide energy for the body’s daily functions and also have other important physiological roles, such as structural and metabolic.
  • Specific healthy dietary patterns, such as the Mediterranean diet, are associated with lower cardiovascular, diabetes, and cancer risk
  • There is not any specific macronutrient breakdown that can either facilitate or complicate weight loss, independent of energy balance
  • Protein is the most important macronutrient for muscle gain and strength goals

Macronutrients are the nutritional components of the food that the body needs for energy and to maintain health and longevity. There are three main types of macronutrients in our diet: proteins, fats, and carbohydrates. All three macronutrients have crucial physiological roles in the body and are all required in a healthy diet for optimal health and function. While energy balance is the most vital variable for weight loss, a balanced macronutrient breakdown should accompany an appropriate energy balance regimen so the individual can also accomplish their exercise goals.


Proteins are made up of basic building blocks called amino acids. Twenty different amino acids link together in various combinations to make up proteins. Eleven amino acids can be synthesized by the body and are known as non-essential amino acids. At the same time, the remaining nine cannot be made by the body and are known as essential amino acids. 


Fats comprise a group of many compounds, including triglycerides, fatty acids, phospholipids, and sterols. However, triglycerides comprise 90-95% of dietary lipids. They are composed of glycerol and three fatty acids. These are three primary dietary fats: saturated, monounsaturated, and polyunsaturated. They have different chemical structures and physical properties. However, their main difference is that saturated fats are solid at room temperature, whereas unsaturated fats are liquid at room temperature.


Carbohydrates are sugar molecules and can be divided into three main types: sugars, starches, and fibers. Sugars are simple carbohydrates (monosaccharides), and their most common dietary form is granulated sugar. Starches and fiber are complex carbohydrates of many simple sugars strung together. Their main difference is that starches are broken down by the body and absorbed for energy, while fiber ends up undigested in the colon, namely the last part of the gastrointestinal tract.

Macronutrients are the human body’s principal energy source; fats’ energy value is 9kcal/g, while proteins’ and carbohydrates’ is 4kcal/g. Apart from being energy substrates, macronutrients have several other physiological roles in the human body.


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Fats’ biological roles

Starting with fat, tissues with a high content of triglycerides, such as subcutaneous and visceral fat, serve as temperature isolators. They also decrease skin permeability to water and prevent its losses. Moreover, fatty acids in the form of phospholipids are the structural components of all cell membranes. Lastly, cell membrane fatty acids are precursors of lipid mediators called eicosanoids. Eicosanoids have many important biological roles in the body, including inflammation mediators, blood flow regulators, thrombosis stimulators, etc.

Proteins’ biological roles

Proteins also serve crucial roles in human physiology. One of their most essential functions is they are enzymes. Enzymes catalyze pathways to produce and break down biological molecules. Relevant examples are food breakdown in the digestive tract, toxin removal by the liver, and hormone production. Proteins also serve as the structural elements of cells and tissues. For example, the structural proteins actin and myosin are responsible for muscle contraction. Moreover, channels that are essential for the transportation of nutrients into and out of cells, as well as nerve signals transduction throughout the body, are proteins.

Carbohydrates’ biological roles

Lastly, carbohydrates are the preferred direct energy source for brain cells, muscle cells, and all other tissues. Carbohydrates also play major metabolic roles, including blood glucose regulation, insulin metabolism, and cholesterol and triglyceride metabolism. Moreover, one of the carbohydrate types, particularly dietary fiber, ensures good gut function by increasing the stool bulk, stimulating intestinal transit, and benefitting the gut microbiota. Some types of dietary fiber are broken down by the gut microbiota, leading to the formation of beneficial bacterial waste products, such as short-chain fatty acids.

How can we know that we consume enough macronutrients so our human body thrives?

Fats’ food sources

Monounsaturated fat is primarily found in olive oil, avocados, nuts, and seeds. Polyunsaturated fat is classified into two major categories: omega-3 and omega-6 fatty acids. Fish oil and fish such as salmon, herring, sardines, mackerel, and trout are the richest food sources of omega-3 fatty acids. On the other hand, vegetable oils, such as safflower, sunflower, soybean, mayonnaise, and margarine, are the richest food sources of omega-6 fatty acids. Saturated fat is mainly found in red meat, full-fat dairy products, butter, and coconut oil.

Proteins’ food sources

High-protein food sources include lean meat, such as chicken breast and lean beef, and low-fat dairy, such as Greek yogurt and cottage cheese, eggs, fish, shellfish, legumes, soy, and quinoa.

Carbohydrates’ food sources

Lastly, nutritious, rich carbohydrate sources include fruits, vegetables, legumes, (sweet) potatoes, and whole grains, such as whole-wheat bread, whole-wheat pasta, brown rice, oats, etc.

A challenging mission for everyone who tries to optimize their health through nutrition is to stick to a dietary regime encompassing the perfect balance of all macronutrients. Is there one out there, though? Healthy dietary patterns can be generally described as those rich in health-promoting foods, such as fruits and vegetables, nuts, whole grains, fish, and soy, and low in animal products, sweets, packaged foods, and white carbohydrates. Such dietary patterns are either naturally occurring in some areas of the world, such as the Mediterranean and Asian diets, or have been developed based on studies of nutrient intake and subsequent health outcomes, such as the DASH (Dietary Approaches to Stop Hypertension) diet.


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The Mediterranean Diet

The primary basis of the Mediterranean diet, which has consistently been shown to reduce cardiovascular, diabetes, cancer, and dementia risk, includes unrefined grains (couscous, bulgur, whole-wheat bread), a variety of fruits and vegetables, low-fat dairy (cheese and Greek yogurt), olive oil, nuts and seeds, legumes, fish, chicken, and eggs.

Asian diets

Asian diets, on the other hand, such as the Japanese and Korean diets, are based on the consumption of rice, fermented foods, such as kimchi and miso, fish, seaweed, fruits, vegetables, and soy and have also been associated with lower risk for metabolic syndrome, obesity, and hypertension.

Weight loss across different macros’ breakdowns

A vast amount of research has also focused on whether there is an ideal macronutrient ratio for weight loss and whether macronutrient breakdown is independent of energy balance for weight loss. Research has concluded that all diets, including low-fat, average-protein (20% fat, 15% protein, 65% carbs), low-fat, high-protein (20%fat, 25% protein, 55% carbs), high-fat, average-protein (40% fat, 15% protein, 45% carbs), and high-fat, high-protein (40% fat, 25% protein, 35% carbs) are equally successful in promoting weight loss and weight loss maintenance given there is a sufficient negative energy balance in each case. Therefore, weight loss is independent of the macronutrient breakdown, and high-protein and high-fat diets, such as the keto diet, are not superior to high-carb diets.

Protein for muscle gain

Although carbohydrates and fats are essential energy substrates and a diet that provides balanced macronutrients assures optimal health, protein is the most critical macronutrient for muscle gain. Although the Recommended Dietary Allowance (RDA) of protein is 0.8g/kg/day, reflecting the minimum amount of dietary protein to meet essential amino acid requirements and prevent muscle mass loss for the entire population, this amount is insufficient for physically active individuals. Protein intake becomes even more important when these individuals are particularly interested in strength and muscle mass gains from the resistance exercises they regularly perform. Therefore, internationally recognized professional organizations, such as the American College of Sports Medicine (ACSM), recommend protein intakes of 1.4-2.0 g/kg/day for physically active individuals. Coupling resistance exercise with post-exercise protein ingestion at ~ 20-30g/day can be even more beneficial for people who follow a regular resistance exercise program and are interested in muscle hypertrophy and strength. Although muscle hypertrophy is more effortlessly accomplished in terms of energy balance, let alone positive energy balance, such high-protein diets (1.6-2.2 g/kg/day) can still support protein balance and muscle gains, provided that the energy deficit does not increase beyond 40% of total energy needs (500-750kcal/day, deficit).

Overall, hitting your everyday macronutrient goals through a healthy and balanced diet with an appropriate energy balance is very important for your overall health and exercise goals. As has already been underlined, breath analysis is the gold standard for determining energy balance. Besides energy balance, breath analysis can also determine an appropriate macronutrient breakdown based on your relative fat/carbohydrate contribution to your daily energy expenditure at rest (resting RER) and your exercise goal. In this way, you can quickly and precisely get your energy balance and macronutrient breakdown goals laid out, thus accomplishing your nutrition and exercise goals more efficiently.


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