Macronutrients are nutrients required in large amounts to provide energy and support the body’s structure and function. The three primary macronutrients are proteins, carbohydrates, and fats. While water and fiber are also classified as macronutrients, they do not contribute significant energy or structural components. This article explores the functions of the main macronutrients and why they are essential for your diet. Much of this information and more can be found in the United States dietary guidelines which you can download here.
Protein plays a critical role in the body by providing energy, contributing to structural integrity, and regulating processes such as DNA replication and hormone production. Each gram of protein contains 4 calories, which the body uses to fuel cellular functions. Protein also supports the formation of collagen, a key structural component of bones, muscles, and skin, and regulates hormones like insulin and human growth hormone.
Proteins are broken down into amino acids, which are categorized as essential or non-essential. Essential amino acids must be obtained through the diet, while the body can synthesize non-essential amino acids if proper nutrition is available. Complete proteins, which contain all nine essential amino acids, are found in animal sources and soybeans. However, plant-based sources can be combined (e.g., beans and rice) to provide a full amino acid profile.
Daily protein intake recommendations vary based on activity level and goals. The Recommended Dietary Allowance (RDA) is 0.8 grams per kilogram of body weight, or about 0.35 grams per pound. For those engaged in weight training or seeking to maximize muscle growth, the recommended intake ranges from 1.6 to 2.2 grams per kilogram of body weight, or 0.73 to 1 grams per pound1. For instance, a person weighing 150 pounds would need about 50 grams of protein daily to meet the RDA, and up to 150 grams to optimally support muscle gain. It's essential to consider all dietary sources of protein, not just animal products, to meet these needs.
Carbohydrates are commonly categorized as simple or complex. Simple carbohydrates, like those found in fruit, are quickly broken down into glucose. Complex carbohydrate foods tend to have more starches and fiber, and also take longer to break down into glucose therefore providing a more sustained energy release. Glucose, the primary energy source for the body, is especially vital during high-intensity activities. Excess glucose that the body consumes but does not need for energy is stored as glycogen for future energy use. Each gram of carbohydrate provides 4 calories.
Current dietary guidelines recommend a minimum of 130 grams of carbohydrates per day to support optimal brain function. Keto diets may promote significantly restricted carbohydrate restriction, as low as 50 grams per day. While there does not seem to be evidence for any major decrease in brain function on this type of diet, it is generally recommended that moderation is better than either extreme. Studies have found that you have a higher mortality risk if your carbohydrate intake was less than 40% of your daily calories or if it was greater than 70% of your daily calories2. Eating carbohydrates not only provides energy but also contributes to fiber consumption which is health promoting3.
Dietary fats, or triglycerides, consist of glycerol and three fatty acid chains. These fatty acids can be monounsaturated, polyunsaturated, or saturated, each with different health implications. Monounsaturated fats are found in olive oil, avocados, and certain nuts, while polyunsaturated fats are present in fish and seeds. Saturated fats are common in beef, pork, butter, and full-fat dairy products. Although saturated fats aren't directly linked to poor cardiovascular outcomes, replacing them with polyunsaturated fats or carbohydrates has been associated with lower cardiovascular event (heart attacks, stroke, etc.) risk4. Trans fats, particularly artificial ones, should be minimized due to their negative impact on heart health.
Fats are crucial for energy, providing 9 calories per gram, and are necessary for the absorption of fat-soluble vitamins. They also play a role in cell membrane structure, brain health, and hormone production. While there's no established minimum fat intake, estimates suggest consuming 40-60 grams per day to avoid hormonal disruptions5. Dropping below that number can affect other body processes such as vitamin absorption and increase the risk of gallstone formation.
A balanced diet that includes proteins, carbohydrates, and fats is helpful for maintaining optimal health. While trends in dieting may emphasize or demonize certain nutrients, a holistic approach that incorporates all macronutrients from whole foods is recommended. If you want further general nutrition advice or to be pointed in the direction of nutrition experts, schedule an appointment with our physical therapists at Maven in Santa Monica.
1. Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A., Devries, M. C., Banfield, L., Krieger, J. W., & Phillips, S. M. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376–384. https://doi.org/10.1136/bjsports-2017-097608
2. Seidelmann, Sara B et al. “Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis.” The Lancet. Public health vol. 3,9 (2018): e419-e428. doi:10.1016/S2468-2667(18)30135-X
3. Ramezani, Fatemeh et al. “Dietary fiber intake and all-cause and cause-specific mortality: An updated systematic review and meta-analysis of prospective cohort studies.” Clinical nutrition (Edinburgh, Scotland) vol. 43,1 (2024): 65-83. doi:10.1016/j.clnu.2023.11.005
4. Hooper, Lee et al. “Reduction in saturated fat intake for cardiovascular disease.” The Cochrane database of systematic reviews vol. 8,8 CD011737. 21 Aug. 2020, doi:10.1002/14651858.CD011737.pub3
5. Whittaker, Joseph, and Kexin Wu. “Low-fat diets and testosterone in men: Systematic review and meta-analysis of intervention studies.” The Journal of steroid biochemistry and molecular biology vol. 210 (2021): 105878. doi:10.1016/j.jsbmb.2021.105878
Speak to one of our team members and book an appointment
