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What Are Macronutrients? Understanding Protein, Carbs, and Fats

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If you’re interested in fitness and nutrition, you’ve likely heard the term macronutrients, aka macros. It seems everyone is concerned about counting macros and calculating their daily intake. So what are macronutrients? Macros are the fundamental nutritional compounds your body needs to function: protein, carbohydrates, and fats.

While some macronutrients get a bad reputation (looking at you, carbs), the truth is that they’re all essential for mental and physical functioning. Depriving your body of any one macronutrient can greatly reduce your performance both in your fitness routine and in everyday life.

Plus, understanding the unique roles of carbohydrates, proteins, and fats in the body can help you better understand and meet your nutritional needs. Here’s what macronutrients are, and how you can fuel your body properly with each one.

What Are Macronutrients?

Humans need large amounts of macronutrients in order to survive. This is because they provide energy, which the body needs to perform life-sustaining tasks like circulation, hormone production, energy synthesis, and digestion.

The energy provided by macronutrients is measured in calories. This is in contrast to micronutrients, which are vitamins and minerals obtained from food.

So how many calories do macronutrients offer? Carbohydrates and protein contribute four calories per gram. This means that one gram of protein equates to four calories. Fats contribute nine calories per gram.

Each type of macronutrient should be consumed in balance, according to your specific needs.

Age, gender, and physical activity level all influence how many macronutrients you need per day.

Counting Calories vs. Macronutrients

The traditional method of losing weight has been to count calories and reduce overall intake of fats and carbohydrates. This makes sense: when calorie intake is lower than calories expended, the body burns fat and weight is lost.

However, counting calories doesn’t account much for the nutritional value of food. For example, a cookie may contain the same amount of calories as a salad, but the macro content of the salad would likely be much healthier because it provides essential fats and proteins.

More and more, people are counting macronutrients to lose weight while still fueling the body properly. The IIFYM (If It Fits Your Macros) diet is one regimen that focuses on macronutrients instead of calories.

Founded by Anthony Collova, IIFYM helps people calculate the number of calories from protein, carbs, and fats they need to lose weight. These calculations are based on basal metabolic rate, activity level, and weight goals. Then, a plan is created to determine a macro limit and meet that limit daily. Here’s a look at each how each macronutrient works in the body.


Carbohydrates are the primary source of energy in the human body. They provide at least 50% of total calories per day. The two main types of carbohydrates are simple and complex.

Simple carbohydrates are composed of small molecules like monosaccharides and disaccharides, which increase blood sugar quickly. In contrast, complex carbohydrates like starches and fiber increase blood glucose levels slowly over time.

Many people tend to look to low-carb diets to lose weight, but most nutritionists stress the importance of including some healthy carbohydrate sources in the diet. When counting macros in your diet, it’s best to reach for complex carbohydrates instead of simple carbohydrates. These keep you fuller for longer, which reduces instances of excess hunger (which leads to calorie consumption and weight gain).


Protein is made up of amino acids, which help build muscle, transport nutrients, and prevent illness, among many other functions. The body requires 20 different amino acids for optimal functioning, 11 of which are created by the body. The other 9 must be obtained through protein sources in food, including meat, dairy, soy, and grains.

Essential amino acids include lysine, tryptophan, phenylalanine, leucine, isoleucine, valine, methionine, threonine and histidine. Ample protein can be found in both animal and plant products, and eating a varied diet can ensure that you get all the required amino acids. This is important to understand because it’s a common misconception that animal sources are the only protein providers.

In fact, high-protein plant foods include seeds, quinoa, beets, avocado, and raw greens. Legumes such as lentils, chickpeas, and black beans are great sources of protein as well. Enough protein can be obtained from a vegetarian or even vegan diet as long as you follow a healthy and macronutrient-dense regimen.


Fats are considered macronutrients because they’re vital for maintaining cell function, boosting brain development, protecting the organs, and boosting nutritional intake from other foods. Fats are composed of fatty acids and glycerol. Essential fatty acids include linoleic acid, an omega-6 fatty acid, and a-Linoleic acid, an omega-3 fatty acid. These are both considered essential because humans can’t synthesize them naturally, meaning they must be obtained from food.

According to the Linus Pauling Institute at Oregon State, “Both omega-6 and omega-3 fatty acids are important structural components of cell membranes, serve as precursors to bioactive lipid mediators, and provide a source of energy.” And both are available from fat as the macronutrient.

Understanding Types of Fats

You’ve probably heard about healthy fats vs. unhealthy fats, the latter of which are found mostly in animal products and processed foods. Eating fat doesn’t always translate to increasing your body fat, however.

Rather, it’s important to understand that unhealthy fats are trans fats, which can lead to weight gain when consumed in large quantities. Consuming too many grams of unhealthy fat per day can also affect a person’s long-term health — increasing the risk of heart disease and stroke while reducing immune system functioning.

What about a low-fat diet? Since 20% of your diet should be comprised of healthy fats, a low-fat diet may not allow for the ample amount of healthy fats required. Focusing only on low-fat foods may also not allow for enough consumption of healthy foods.

Even if you do follow a low-fat diet, it’s important to obtain most of your fats from lean, unsaturated sources. Examples include avocados, almonds, walnuts, and seeds. Oils are also a source of healthy fats, and vegetable oils like olive oil and coconut oil can be incorporated into cooking to boost healthy fat intake and support weight loss.

Understanding Macronutrients and Making Healthy Food Choices

Macronutrients are the building blocks of the human diet. Carbohydrates, protein, and fats are all considered essential because they keep our body healthy and functioning properly.

Carbohydrates work to provide us with energy, so we can fuel bodily systems like digestion and hormone production. Proteins also give us energy, and they help us manage the repair and growth of tissue so we can continue to perform at optimum levels. Fats, though often associated with negative implications, are essential for both our brain and organs.

Counting macronutrients instead of calories may be a smarter way to stay on top of your nutrition and maintain a healthy weight. By making macronutrient-rich food choices, you can better energize your body and ward of instances of deficiency and disease.

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