What Are Macronutrients? A Complete Scientific Guide

Chances are, the words "protein," "fat," and "carbohydrates" are common ones in your vocabulary. But have you heard of “macronutrients”?

For those new to the term, macronutrients are the “big three” nutrients: protein, fat, and carbohydrates that are key in our diets.

“Macronutrients are essential nutrition components that are needed in larger quantities by the human body,” explains Julie Stefanski, RDN, a spokesperson for the Academy of Nutrition and Dietetics who practices in York, Pennsylvania. Hence the word “macro” as opposed to “micro,” in “micronutrients.”

While the term “macronutrients” (or more popularly recently, “macros”) has been around for a while, it’s only recently gotten a lot of buzz. That’s because more people are counting their macros rather than calories, whether to lose weight or potentially improve their health (with celebrities like Hilary Duff, or the trainer at your gym, getting in on the trend). Counting macros is also an element of certain popular diet plans such as keto, where followers count fat, protein, and carbs with the hope of achieving various touted health benefits, weight loss among them.

Here, discover what you need to know about macronutrients, and whether you should start putting them on your radar.

Ready for a little macronutrient 101? “The three macronutrients our body requires are carbohydrate, protein, and fat,” says Christine M. Palumbo, RDN, a nutrition consultant from Naperville, Illinois. “Each of these play a different, vital role in the body — working together, they keep our bodies’ various functions, such as growth, reproduction, digestion, and movement, humming along,” Palumbo adds.

Energy is also a key role of macronutrients, explains Stefanski. “Macronutrients such as fat, protein, and carbohydrates provide energy for our cells, while vitamins and minerals, the micronutrients, do not,” says Stefanski.

Macronutrients are typically measured in grams, according to Cleveland Clinic, and some people keep track of how many grams of each macronutrient they consume in a day.

If you were to rank nutrients in the order of their importance, macronutrients would be at the very top of the list. They’re that vital for your body.

Macronutrients provide energy, but their job doesn’t stop there. “Each essential macronutrient has functions in the body besides providing energy,” says Stefanski. On top of that, foods that contain macronutrients also provide vitamins and minerals, Stefanski adds.

The three key macronutrients — protein, carbohydrates, and fat — are all considered essential nutrients (and according to Washington State University, vitamins, minerals, and water are also essential nutrients). These six nutrients are deemed “essential” because you need them in order for your body to function as it should; plus, you have to get these nutrients from the food you eat (and the things you drink!). Your body can’t make them on its own.

“The term ‘macro’ means large and ‘micro’ means tiny — we need large amounts of the macronutrients of carbohydrates, fats, protein and water and tiny amounts of vitamins, minerals and phytochemicals,” says Palumbo.

According to the Cleveland Clinic, macronutrients are like the main characters, and micronutrients are the supporting cast in your diet, with each character important to the performance.

You’re probably familiar with the names of many micronutrients. “The most abundant micronutrients in the body include calcium, sodium, potassium, and magnesium,” says Stefanski. “These minerals are measured in milligrams, compared to macronutrients, which are measured in grams,” she adds. Meanwhile, Stefanski says, some micronutrients, like certain vitamins, are measured in extremely tiny units called “micrograms.”

All micronutrients are crucial for the body, helping prevent diseases and improve well-being, the Centers for Disease Control and Prevention (CDC) notes.

Whether it’s micronutrients or macronutrients, the best way to get them is by eating a wide array of healthy, fresh whole foods, rather than taking them in supplement form, notes the Ohio State University.

There are three key macronutrients: fat, protein, and carbohydrates, and, plain and simple, you need each to function. Here’s the lowdown on what each does in your body.

Fat

Fortunately, fat is no longer the shunned macronutrient. “One of the three key macronutrients, fat supplies energy — or calories — is part of many of our body’s cells, and supports our many metabolic functions like growth and the transport of nutrients,” explains Palumbo.

Whether it’s olive oil or wild-caught salmon, chances are you’ve heard doctors or dietitians singing fat’s praises lately. “Our bodies need essential fatty acids that compose the fats and oils we are familiar with,” says Palumbo.

The type of fat you choose in your diet matters. Ideally you’ll want to skip or limit the “bad fats” like saturated fats and trans fats, according to the American Heart Association, which can raise LDL or “bad” cholesterol in your body (saturated fats are found in foods like bacon and sausage, while trans fats are sometimes found in processed foods).

Instead, choose mono- and polyunsaturated fats, which can improve your cholesterol, according to the Mayo Clinic, and may lower your odds of heart disease and stroke. You can get monounsaturated fats in olive oil and avocado oil, and many nuts, the Mayo Clinic notes, while fish and flaxseed contain polyunsaturated fats.

Getting enough fat in your diet shouldn’t be so hard to do. “The vast majority of foods contain at least a little bit of fat — and of course, the healthiest sources come from plants,” says Palumbo. “Plant-based fats and oils are derived from grains, vegetables, nuts and legumes,” Palumbo adds.

How Much Fat Do I Need?

According to the U.S. Department of Agriculture (USDA) Dietary Guidelines for Americans, women ages 31 to 50 should aim for 20 to 35 percent of their calories from fat. That means if a woman is eating 1,800 calories per day, she should shoot for 360 to 630 calories from fat.

If someone is tallying their macros by counting grams (g), they would want 40 to 70 g of fat. According to the Cleveland Clinic, fat has 9 calories per gram.

Also, if you are eating lots of healthy fats, you may want to bump up how much you take in. “Research focused on reducing heart disease using the Mediterranean eating pattern showed that a regular eating pattern made up of 35 to 40 percent of calories from mainly monounsaturated fat sources can be beneficial in reducing inflammation and disease risk,” says Stefanski. (Find some examples of this type of fat below.) Past research shows that a Mediterranean diet improved study participants' overall health status, with a reduction in mortality.

In addition to using olive oil liberally in your cooking, you might also want to visit your fishmonger regularly. “Many health authorities recommend consuming fatty fish two to three times per week in order to reap the health benefits of omega-3 fats,” says Stefanski (and omega-3s are a type of good-for-you polyunsaturated fat).

What Are the Best Sources of Fat?

According to the Harvard T.H. Chan School of Public Health and Palumbo, you have many healthy fats at your disposal. The two main types are polyunsaturated and monounsaturated. Here are some sources of each type of healthy fat.

Monounsaturated Fat

• Olive oil
• Peanut oil
• Canola oil
• Almonds
• Pecans
• Hazelnuts
• Pumpkin seeds and pumpkin seed oil
• Sesame seeds and sesame seed oil
• Avocados and avocado oil

Polyunsaturated Fat

• Walnuts
• Salmon
• Tuna
• Herring
• Sardines
• Anchovies
• Mackerel
• Black cod
• Flaxseed and flaxseed oil
• Canola oil (contains both mono- and polyunsaturated fat)

Protein

There’s a reason why so many people are on protein-packed diets these days. “The macronutrient protein plays many important roles in the body — it’s considered a building block of life, and it’s involved in the formation of everything,” says Palumbo.

Protein is found almost everywhere — in our bones, muscles, hair, skin, and the list goes on, Harvard T.H. Chan School of Public Health notes. “Protein, made up of different types of amino acids, builds, repairs and maintains our body’s tissues,” says Palumbo. Amino acids are molecules that join together to form proteins, and the body uses these to do things like help the body grow and break down food, according to MedlinePlus.

How Much Protein Do I Need?

The USDA suggests 10 to 35 percent of a person’s daily calories come from protein. That means if a person is on a 1,800 calorie diet, they would want to shoot for around 180 to 630 calories from protein or 45 to 158 g of protein per day. The Cleveland Clinic notes that protein has 4 calories per gram.

Harvard T.H. Chan School of Public Health, meanwhile, suggests aiming for 7 g of protein for every 20 pounds of body weight. So, if a person weighs 200 pounds, the daily goal would be to get 70 g of protein.

Your target amount of protein may be different, too, depending on if you’re pregnant or the style of eating you’re following. For example, some people might be on a high-protein diet in an effort to lose weight. Some research, published in September 2020 in the Journal of Obesity and Metabolic Syndrome, shows that eating in this way may potentially help people shed pounds. Another study, published in May 2022 in the journal Obesity, found that higher amounts of protein when you’re on a calorie-restricted diet could improve your diet quality and prevent muscle loss.

To find the right target for you, consider consulting your dietitian or physician.

And with so many protein powders and products on the market, you might be concerned you’re getting too much. “Excess protein does contribute to our calorie intake — it’s not simply eliminated from the body — so if you’re eating more protein than needed, it can contribute to weight gain,” says Stefanski. The Mayo Clinic also notes that too much protein also could lead to a greater risk of heart disease, especially if your protein source contains lots of saturated fat.

What Are the Best Sources?

According to Palumbo, here are some of the best sources of healthy protein (also, Stefanski adds that some protein is also found in vegetables and grains).

• Beans
• Fish
• Eggs
• Dairy or soy milk
• Tofu
• Skinless poultry
• Nuts

Carbohydrates

Calling all carb fans! Carbs play a crucial role in your body, serving as your body’s primary energy source, says Palumbo.

As a primer, your body breaks down carbohydrates into glucose, or blood sugar, and that helps fuel your organs, tissues and cells, notes MedlinePlus. The are three main types of carbohydrates, per the agency.

1. Sugar, which is a simple carbohydrate (think the sugar in desserts and soda)
2. Starch, which is a complex carbohydrate (and found in pasta and veggies like potatoes)
3. Fiber, which is also a complex carbohydrate (and found in many plant-based foods like veggies, fruits, nuts and beans)

“Carbohydrates can be found in highly processed foods — often called ultra-processed foods — and in natural food sources,” says Stefanski. “Often, less-processed foods, such as whole grains, provide more fiber and nutrients,” Stefanski adds. And, according to Harvard T.H. Chan School of Public Health, a diet high in fiber may lower your risk of heart disease and diabetes.

How Much Carbohydrate Do I Need?

The USDA suggests a whopping 45 to 65 percent of your calories each day come from carbohydrates.

That means that for a person on a 1,800-calorie diet, you’d want to aim for 810 to 1,170 calories a day from carbohydrates. If you’re counting your carbohydrates in grams, then that equals about 203 to 293 grams of carbohydrates per day. (FYI, carbohydrates contain 4 calories per gram, notes the USDA.)

Ideally, you’ll want to make sure your carbohydrates come from good-for-you sources, and that you’re getting plenty of fiber. “Most Americans are missing out on the many benefits that come from consuming enough insoluble and soluble sources of fiber,” says Stefanski, and as the American Society for Nutrition reported in June 2021.

What Are the Best Sources of Carbs?

Here are some of the best ways, Stefanski suggests, to get healthy sources of carbohydrates.

• Vegetables (sodium-free or low-sodium canned and frozen also count)
• Fruits with the skin on (sugar-free canned and frozen count)
• Whole-grain foods such as bread, cereal, and pasta
• Milk
• Milk products (like yogurt)

Chances are, you’ve heard someone in your friend circle talk about how they’re “counting macros.” So, what diets are involved? “The most common use of macronutrient counting is for diabetes or other lower-carbohydrate diets,” says Stefanski.

When it comes to diabetes, people count macros typically when it comes to their carbohydrate intake. “Carbohydrates have the biggest impact on our blood sugar level, and counting how many carbohydrates are consumed in one sitting can help prevent blood sugar levels from rising to the point that it causes damage to the body,” says Stefanski. And one study published in July 2019 in the journal Diabetologia found that if people with type 2 diabetes reduce their carbohydrate intake and increase their fat and protein, it may help them better regulate their blood sugar levels.

People may also count their macros on a ketogenic diet. That’s in part because people must keep their carbohydrates to a very minimal amount, while aiming for a high amount of fat (and moderate amount of protein), according to Harvard T.H. Chan School of Public Health.

Then there are diets that involve counting macros that are geared specifically to shedding pounds. “The macro diet has been around for some time; popular for weight loss, it involves identifying the number of macronutrients your body needs and counting them daily,” says Palumbo. “While it isn’t for everyone, some people swear by it and find success — instead of counting calories, people count macros,” Palumbo adds. Some companies have attempted to put new spins on the “counting macros” diet, such as the If It Fits Your Macros, which, in theory, helps people find their personalized macro targets for weight loss.

But before you start counting macros on your own, know this: “Ideal macronutrient levels need to be personalized for optimal health, and working with a registered dietitian-nutritionist can help you pinpoint what level of each macronutrient is best for you,” says Stefanski.

Also, know that many styles of eating can lead to a healthy body. For example, one study published in January 2020 in the International Journal of Cardiology found that three diets that each focused on a different macronutrient (such as emphasizing protein, monounsaturated fats, or carbohydrates) helped lower the study participants' cardiovascular risk. The key to reducing a person’s odds was a healthy diet, the study authors note, rather than any one macronutrient.

“A balance is needed between macronutrients, and since macronutrients provide energy, consuming too much of any one nutrient may provide more calories than the body uses on a daily basis,” says Stefanski. That means if you are focused on, say, getting high levels of protein, you may inadvertently be taking in more calories than you need.

An easy way to hit macro targets without a lot of stress or hassle? Consider Palumbo’s advice. “Follow the MyPlate graphic created by the United States Department of Agriculture. It takes the muss and fuss of trying to determine grams and ounces away from you, and it works so well,” says Palumbo. The MyPlate graphic visually depicts a plate with vegetables and fruit taking up half the plate, with whole grains and protein taking up the other half.

Now, you might be wondering how water and alcohol fit in. “Keep in mind that water is also an essential nutrient — without water, we die after a few short days. While it doesn’t provide calories, it is essential to life,” says Palumbo. Also, Stefanski adds, alcohol is a macronutrient, but it’s not considered an essential nutrient. Alcohol provides 7 calories per gram on its own and then additional calories are provided in an alcoholic beverage by carbohydrates, Stefanski adds. (Fat contains the same amount of calories, the National Health Service in the United Kingdom notes.)