What Are Macronutrients?
Macronutrients — often called "macros" — are the three main categories of nutrients your body needs in relatively large amounts to function: protein, carbohydrates, and fat. Unlike micronutrients (vitamins and minerals), which are needed in small doses, macronutrients supply the calories your body uses for energy, repair, and structural support.
Macronutrient
One of the three major nutrient categories — protein, carbohydrates, and fat — that the body requires in large amounts to produce energy and support essential functions.
Essential amino acids
The nine amino acids the human body cannot synthesize on its own and must obtain through food. They are critical for protein synthesis, tissue repair, and other metabolic processes.
Complete protein
A protein source that contains all nine essential amino acids in adequate amounts. Most animal-based proteins are considered complete.
Dietary fiber
A type of complex carbohydrate found in plant foods that the body cannot fully digest. It supports digestive health, blood sugar balance, and has been linked to heart health benefits.
Unsaturated fat
A type of dietary fat — including monounsaturated and polyunsaturated varieties — found in foods like olive oil, avocados, and fatty fish. Research generally associates these fats with cardiovascular health when consumed as part of a balanced diet.
Glucose
A simple sugar that serves as the body's primary fuel source, particularly for the brain and muscles. Carbohydrates are broken down into glucose during digestion.
Each macronutrient provides a specific number of calories per gram: protein and carbohydrates each provide 4 calories per gram, while fat provides 9. These numbers underpin how food labels calculate total calorie counts — which you can explore further in our guide to reading a nutrition label.
No single macronutrient is inherently good or bad. Each plays distinct, essential roles, and eliminating any one of them entirely from your diet is generally not supported by nutrition science. This article gives you a clear, evidence-based overview of what each macro does and where to find it.
Protein: The Body's Building Block
Protein is made up of smaller units called amino acids, which the body uses to build and repair muscle tissue, produce enzymes and hormones, and support immune function. Of the 20 amino acids, 9 are considered essential — meaning your body cannot manufacture them, so they must come from food.
Common food sources of protein:
- Animal-based: chicken, fish, eggs, dairy, beef, pork
- Plant-based: lentils, chickpeas, black beans, tofu, tempeh, edamame, quinoa
- Nuts and seeds: almonds, pumpkin seeds, hemp seeds
Animal proteins are generally considered complete proteins — they contain all 9 essential amino acids in sufficient amounts. Many plant proteins are incomplete, but combining a variety of plant foods throughout the day can meet your full amino acid needs.
| Calories per gram of protein | 4 kcal/g (USDA Dietary Guidelines) |
| Calories per gram of carbohydrate | 4 kcal/g (USDA Dietary Guidelines) |
| Calories per gram of fat | 9 kcal/g (USDA Dietary Guidelines) |
| Essential amino acids | 9 (National Academies of Medicine) |
| Fat-soluble vitamins requiring dietary fat for absorption | A, D, E, K (NIH Office of Dietary Supplements) |
| General protein baseline for sedentary adults | 0.8 g per kg body weight (National Academies of Medicine Dietary Reference Intakes) |
Protein needs vary based on age, activity level, body size, and health status. The Dietary Reference Intake established by the National Academies of Medicine suggests a general baseline of 0.8 grams per kilogram of body weight for sedentary adults, but individual needs may differ. A registered dietitian can help determine what's appropriate for you.
Carbohydrates and Fat: Energy and Beyond
Carbohydrates are the body's preferred and most efficient energy source. They break down into glucose, which fuels the brain, muscles, and organs. Carbohydrates fall into two broad categories:
- Simple carbohydrates: sugars found naturally in fruit and dairy, or added to processed foods (table sugar, syrups)
- Complex carbohydrates: starches and fiber found in whole grains, legumes, vegetables, and potatoes
Fiber — a type of complex carbohydrate that the body cannot fully digest — is associated with digestive health, blood sugar regulation, and cardiovascular benefits according to established nutrition research. Whole food sources of carbohydrates generally provide more fiber and micronutrients than refined alternatives.
Fat is essential for absorbing fat-soluble vitamins (A, D, E, and K), producing hormones, protecting organs, and supporting brain health. Dietary fats are categorized by their chemical structure:
- Unsaturated fats (monounsaturated and polyunsaturated): found in olive oil, avocados, fatty fish, flaxseed, and nuts — generally associated with cardiovascular health in research
- Saturated fats: found in butter, full-fat dairy, red meat, and tropical oils — current dietary guidelines suggest limiting intake
- Trans fats: primarily from partially hydrogenated industrial oils — largely removed from the U.S. food supply due to health concerns, but still present in trace amounts in some products
For a deeper look at how these nutrients appear on food packaging, see our guide to macronutrients explained.
This article is for general informational and educational purposes only and is not a substitute for personalized medical or nutritional advice. Consult a qualified healthcare professional or registered dietitian for guidance specific to your health needs.
The content on this site is provided for informational purposes only and should not be considered a substitute for professional advice. While we strive to provide accurate and up-to-date information, we make no guarantees regarding its completeness or accuracy. Always consult a qualified professional for advice specific to your circumstances before making any decisions.