The Differences and Similarities Between Carbohydrates, Lipids and Proteins

Carbohydrates, lipids and proteins make up the three macronutrients. You need to eat a lot of these macronutrients each day, and their requirement is higher than that of micronutrients, aka vitamins and minerals.

All macronutrients are organic compounds composed of carbon, hydrogen, oxygen and sometimes other elements. As potential calorie sources, they can be oxidized to produce ATP, the body's main source of energy, according to an older 2010 report in ‌Nature Education‌.

Sugars and starches are the main digestible carbohydrates, and they provide glucose for energy production. The body stores extra glucose as glycogen.

Glucose can fuel intense, short bursts of activity and it is also necessary for brain function. If your body doesn't have much glucose to burn, it converts fats and protein into energy, according to LibreTexts.

Fiber is another type of carbohydrate. While it only offers minimal, inefficient energy, it plays an important role in keeping the digestive system healthy, according to the Academy of Nutrition and Dietetics.

The two main dietary lipids are fats/oils and cholesterol. Lipids are also the major component of cell membranes and they help protect the organs.

Fats also store energy and become a reserve fuel source, per a May 2021 ​‌StatPearls‌​ report. If your cells don't get enough glucose, your body burns fat for energy instead — this process creates ketones, according to the U.S. National Library of Medicine (NLM).

Healthy lipids include unsaturated fats, like polyunsaturated fats and monounsaturated fats, which can help improve your blood cholesterol levels when eaten in moderation and used in place of unhealthy lipids such as saturated and trans fats, per the American Heart Association (AHA).

Cholesterol does not supply calories, but it is a building block of very important chemicals such as vitamin D.

Remember, both lipids and carbohydrates play an important role in delivering energy to cells. When you eat carbs, they are quickly broken down into glucose, which fuels all muscle action. Carbohydrates can also be stored as glycogen in the muscles and liver for later use. Lipids are either stored in various fat cells throughout the body for later energy use or in the liver, per Oregon State University.

One similarity between carbohydrates and lipids is that they cannot be converted to protein.

Protein is composed of building blocks called amino acids. Protein's primary function is to build and maintain body structures, such as muscle, bones and internal organs, and to synthesize important molecules such as antibodies, enzymes, neurotransmitters and various blood proteins, according to the NLM.

Proteins differ from the other energy nutrients because they contain an element not found in carbohydrates and fats — nitrogen, according to the Cleveland Clinic. Some proteins also contain sulfur.

When you eat protein-rich foods, digestive enzymes break down those proteins into single amino acids, which are absorbed into your bloodstream. Aside from acting as the building blocks of body structures, amino acids also fill other roles.

Some amino acids help build neurotransmitters, which chemical signals from nerve cells to other cells. For example, the amino acid tyrosine helps produce epinephrine, a neurotransmitter that plays a role in your body's "fight or flight" response, per the Cleveland Clinic.

Protein can be used for energy, but it's not the body's preferred source (carbs are!). What's more, lipids, carbohydrates and protein are similar in the way that if you eat too much of them, they can be stored as fat.

Even though all of the macronutrients can supply energy, a balanced diet providing all three will help the macros to perform their unique functions.

And foods that provide macronutrients are also sources of important micronutrients as well.

The Institute of Medicine sets forth dietary standards called the Acceptable Macronutrient Distribution Ranges, which recommend that 45 percent to 65 percent of your total calorie intake comes from carbs, 20 percent to 35 percent from fat and 10 percent to 35 percent from protein.

Though flexible, these ranges help ensure you get enough of each macro daily.