Macronutrients are compounds your body needs in large amounts to function properly. You see them listed as carbohydrates, proteins and fats on food labels. Over time, a severe deficiency in any of these nutrients can compromise your energy levels, growth and eventually your ability to survive.
Carbohydrates are the body’s primary source of energy. The Institute of Medicine recommends that 45 to 65 percent of your daily calories come from this nutrient. Your body converts carbohydrates into sugars that it can burn immediately for energy or to store in the muscles. Without adequate carbohydrates, you might feel fatigued and weak, as your body must look to other less-efficient sources of fuel. Severe depletion in carbohydrates can deprive the kidneys, brain and heart the energy they need to function. Without enough fiber, a type of carbohydrate that your body cannot digest, you might experience constipation and hemorrhoids. Too little fiber could also increase your risk of certain cancers and heart disease.
While saturated fats and trans fats can raise your risk of heart disease, healthy fats found in plants called "unsaturated fats" are essential for many body functions. Without adequate fat, you might experience dry skin and hair. You may be hungry more often because fat takes longer to leave the stomach than either protein or carbs, thus helping to keep you feeling satisfied. For you to absorb vitamins A, D, E and K and nutrients called "carotenoids," you must consume some dietary fat. Omega-3 fats -- found in fatty fish, walnuts and flaxseeds -- reduce your risk of heart disease. If you do not get enough of these healthy fats, you may find yourself at a higher risk for coronary artery disease. The Institute of Medicine recommends you consume between 20 and 35 percent of your daily calories from healthy fats.
You need the amino acids that come from proteins to support growth, tissue repair, immunity, hormone and enzyme production, and the preservation of lean muscle mass. The Institute of Medicine recommends consuming between 10 and 35 percent of your daily calories from protein. True protein deficiency is rare in the United States, but it can cause decreased muscle mass, diarrhea, failure to thrive, diminished immunity, a protruding belly and fatigue.
Most diets that include a variety of foods from the dairy, meat, vegetable, fruit and grain food groups provide you with an adequate amount of macronutrients. If you are on a diet that limits your macronutrient intake, such as a low-carb diet or a low-fat diet, check with your physician to be sure you are still getting amounts that are adequate for your needs. Many times, these limiting diets are unsustainable because they lead to fatigue or nutrient deficiencies. Vegetarians and vegans should take extra care to plan their diets to include adequate amounts of protein from nonanimal sources, such as beans, nuts and seeds.