Updated 14th March 2024

Carbohydrate, fat, protein: Your guide to macronutrients

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Macronutrients are the nutrients in food that your body needs in large amounts: carbohydrates, fat, and protein. These nutrients give you energy and keep your body systems functioning.

In this article, you can find out why carbohydrates, fat, and protein are important for your body, what the best sources of macronutrients are, and why looking at the quality of your diet as a whole is better for your health than focusing on specific macronutrients.  

What are macronutrients?

The nutrients available in food are categorized into two groups, based on how much your body needs: macronutrients and micronutrients. 

Macronutrients are needed in large amounts. Carbohydrates, fat, and protein are macronutrients. Micronutrients, however, are needed in smaller amounts, and these include vitamins and minerals. 

Macronutrients provide your body with energy. But they are also crucial for many other things, like insulating you against cold temperatures, making sure that all the cells in your body work, and feeding the microbes in your gut. 

What are carbohydrates? 

Carbohydrates are molecules that your body uses as its main source of energy. They are vital for a healthy diet.

Carbohydrates supply your body with glucose, which your cells use as fuel. Certain complex carbohydrates, like fiber, also feed your gut microbiome.

These molecules can be found in a wide variety of foods, but not all sources are the same when it comes to your health. 

There are three main types of dietary carbohydrates, and they have different functions in your body:  

1. Sugars

Sugars, like glucose, fructose, and sucrose, are simple carbohydrate molecules. They are easily absorbed by the cells around your body, which use them for fuel. 

2. Starches

Starches are complex carbohydrate molecules. They take longer to digest because your body must break them down into simple sugars before your cells can use them for energy. This means that the energy from starches is released more steadily into the blood. 

3. Fiber

Fiber is a type of carbohydrate molecule that humans can’t digest. There are lots of different types of fiber molecules.

The microbes in your gut break down fiber into short-chain fatty acids (SCFAs). These are important for your health and help with blood sugar, blood fat, and appetite control, and they feed your microbiome to boost your immune system. 

Learn more about your gut microbiome and why it’s important for your health here.

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Best sources of carbohydrates

Research suggests that unprocessed or minimally processed foods are the healthiest source of carbohydrates.

This is because they typically have a mix of sugars, starches, and fiber, plus vitamins, minerals, and many other powerful plant antioxidants known as phytonutrients, which help prevent inflammation. 

How much a food has been processed can make a difference to your health. Ultra-processed foods are usually less nutrient dense and have high amounts of added sugars, salt, unhealthy fats, and chemical additives, with few valuable nutrients. 

For example, the carbohydrates from the apples in a slice of apple pie have been broken down, and additional ingredients like sugar and butter have been added. This does not come with the same health benefits as eating a whole apple, which has a higher ratio of fiber and starch to sugar.

In other words, sources of simple carbohydrates, such as whole fruits and milk, provide you with a number of different nutrients. But refined carbohydrates, such as those found in table sugar, only supply your cells with energy.

High-quality sources of carbohydrates are:

  • whole grains

  • fruits

  • vegetables

  • legumes (beans and pulses)

  • nuts and seeds

Choosing high-quality carbohydrates that feed you and your gut microbes is important for your health. ZOE’s research, which includes the largest nutritional study of its kind, shows that no two people respond to food in the same way. 

That’s why the best carbohydrates to eat as part of your diet will be unique to you. 

What is fat?

Fat is another important nutrient that is essential for your health. Fat molecules, also known as triglycerides, contain glycerol — which is a sugar alcohol — and three fatty acids. 

Just like carbohydrates, fat can provide your body with energy. It also acts as insulation to keep you warm, is required for absorption of fat-soluble vitamins A, D, E, and K, and is a source of essential fatty acids, like omega-3.

Your body can’t make omega-3 itself, but it is important for healthy brain function. In fact, every cell in your body needs fat to function properly

There are three main types of dietary fat:

1. Unsaturated fat 

Unsaturated fat is liquid at room temperature and is generally considered a healthy fat. There are two types of unsaturated fats, monounsaturated and polyunsaturated. Omega-3 is a type of polyunsaturated fat. 

Research suggests that regularly consuming unsaturated fat can provide a variety of health benefits, such as promoting heart health and reducing the risk of death

2. Saturated fat

Saturated fat is solid at room temperature and is typically found in animal products and some plants. Saturated fat has long been associated with an increased risk of heart disease, inflammation, and unhealthy cholesterol levels. 

But the science is not straightforward. More recently, research has called the link between saturated fat and heart disease into question.  

3. Trans fat

Artificially made trans fat is made by processing vegetable oil. It is also known as partially hydrogenated oil. 

Small amounts of naturally occurring trans fats can be found in beef and dairy fat. 

Consumption of trans fat is linked to health complications, such as unhealthy cholesterol levels, an increase in inflammation, and insulin resistance. 

The use of partially hydrogenated oil is now banned in the U.S. In the U.K., trans fats are still found in many ultra-processed and fast foods

Best sources of fat

Your body needs fat to function, but quality is key. Fats that have been processed can change the way your body responds to food.  

Unsaturated fats are the healthiest option. While research is changing the way some experts view saturated fats, sticking to moderate amounts is in line with official dietary guidelines.  

Low-fat dairy products often contain added sugar, which may contribute to excess weight and interfere with blood sugar control. Opting for full-fat dairy, even though it has saturated fat, can often be healthier than the low-fat alternatives.

Sources of healthy fats are:

  • nuts

  • seeds

  • vegetable oils

  • oily fish such as trout and mackerel

  • avocado

  • moderate amounts of full-fat dairy

How your body responds to fat is unique and down to factors including your gut microbiome, age, weight, and whether you live with a chronic condition. 

The ZOE at-home test kit analyzes your blood fat in combination with your blood sugar and microbiome to help you identify the best foods for you. 

What is protein?

Proteins are molecules that are made from long chains of amino acids. They are essential for your health and do several jobs around your body.   

Enzymes are proteins that drive chemical reactions in your cells and organs. Proteins are also needed to make other compounds, like neurotransmitters, hormones, and antibodies. 

Like carbohydrates and fat, protein can also provide energy, but the best use of protein is in cell building and repair. This is particularly important after exercising. 

An adequate protein intake is an important part of a balanced diet.

There are over 20 amino acids combining in different ways to make the millions of proteins in your body. Nine of these amino acids are considered essential amino acids, meaning your body can’t make them. You must get them from food. 

There are two different types of protein sources:

1. Complete proteins

Complete proteins have all nine essential amino acids and are mostly animal proteins, such as beef, chicken, and fish. There are also a few plant options, such as quinoa and soy.

2. Incomplete proteins

Incomplete proteins are missing one or more essential amino acids. These include mostly plant sources, such as beans and pulses, seeds, nuts, and whole grains. To get all the essential amino acids, you need to eat a variety of these foods.

Best sources of protein

As with carbohydrates and fats, minimally processed, high-quality protein sources are the best option.

High-quality sources of protein include:

  • tofu

  • beans

  • eggs

  • nuts and seeds

  • legumes

  • dairy

  • fish

  • tempeh

With the ZOE program, you can find out the best protein-rich foods to eat in combination for your body. 

Diet quality is key

If you’ve ever had a surge of guilt after eating your favorite sweet treat or indulgence, you’re not alone. But contrary to what your emotions may be telling you, the occasional less-than-healthy meal is typically not something to stress over. 

Rather than obsessing over every bit of food or drink you put in your mouth, focus on your overall diet quality

ZOE’s research shows that each person’s response to food is unique and that a personalized approach is better than one-size-fits-all recommendations. 

With ZOE’s at-home kit, you can discover how you react to different foods and find out what types of food combinations work best for your body.

Focusing on diet quality takes a wider scope than the latest fad diet. It allows you to look at your overall dietary intake, rather than counting each individual component of a meal. 

A healthy diet should be rich in high-quality plant-based foods, such as whole grains, vegetables, fruit, nuts and seeds, as well as fermented foods that are good for the gut microbiome. These give your body all the macronutrients it needs.

At ZOE, we believe that no food should be off-limits and that the occasional indulgence forms part of a healthy diet.  


Macronutrients — carbohydrates, fat, and protein — are nutrients found in foods that your body needs in large amounts. These nutrients provide energy and are required for many bodily functions and movements. 

For the best results, focus on eating an overall high-quality diet, rather than tracking specific amounts of macronutrient intakes.

Each person has a unique response to different foods. Discovering your individual needs allows you to eat for your health instead of trying to conform to generalized, sweeping diet recommendations.

Take our quiz to learn more about how ZOE can help you understand how your body responds to the foods you eat.


Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. The Lancet. (2017).


Association of specific dietary fats with total and cause-specific mortality. JAMA Internal Medicine. (2016).


Biochemistry, essential amino acids. (2021).


Biochemistry, Lipids. StatPearls. (2021).


Carbohydrates. (n.d.).


Dietary fats and cardiovascular disease: A presidential advisory from the American Heart Association. Circulation. (2017).


Dietary guidelines for Americans 2020-2025. (n.d.).


Fats and cholesterol. (n.d.).


Fat-soluble vitamin. (n.d.).


Final determination regarding partially hydrogenated oils (removing trans fat). (2018).


Quinoa. (n.d.).


The impact of dietary fatty acids on human adipose tissue. Proceedings of the Nutrition Society. (2019).


Trans Fats


Types of fat. (n.d.).


What are interesterified fats and should we be worried about them in our diet? Nutrition Bulletin. (2017).


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