Protein, fats and carbohydrates are the three macronutrients that provide calories that your body can convert into energy. Your body also needs water and micronutrients for survival; micronutrients are vitamins and minerals that you need in small amounts. According to the U.S. Department of Agriculture, the majority of your diet should be carbohydrate-based -- up to 65 percent of your calories might come from carbs. Between 25 and 35 percent of your calories should come from fat and 10 to 35 percent from protein.
Protein
Every cell in your body contains protein, as do most of your body's fluids with the exception of bile and urine. When you eat foods high in protein -- meat, seafood, poultry, eggs, legumes, dairy products, tofu, nuts and seeds -- your body breaks them down into amino acids, "the building blocks of life," according to the National Institutes of Health. These amino acids are used to repair cells and create new ones and are critical for growth during pregnancy, childhood and adolescence.
Fats
There are three main types of fats: unsaturated, saturated and trans fats. Saturated fats and trans fats are the types closely linked to high cholesterol and an elevated risk of cardiovascular disease. Some fat is essential to your diet, however. Your body uses dietary fat for energy, brain development in infants and children and to absorb fat-soluble vitamins. Fat in food signals your brain that you have eaten enough, providing taste and a feeling of satiety. Unsaturated fats include vegetables oils and are usually liquid at room temperature. Fats that are solid at room temperature, such as butter or lard, are usually saturated fats. Trans fats most often are man-made, turning an unsaturated fat into a saturated one, such as margarine. Fats have 9 calories per gram; following a 2,000-calorie diet, expect to consume 500 to 700 calories from fat.
Carbohydrates
Your body turns carbohydrates into glucose, your primary source of energy. Glucose that's not used right away is stored as fat for later use. Carbohydrates are typically found in plant foods and dairy products. There are two types of carbs. Simple carbs are quickly converted to glucose, while complex carbs take longer. Sugars, including natural sugar in fruit and dairy, are simple carbs and can flood your bloodstream with glucose. Fiber and starch are complex carbs, which slow digestion and supply a steady stream of glucose. The majority of your carb choices should be complex carbs: vegetables, legumes, fruits and whole grains. Refined grains act more like simple carbs, because the fiber has been removed. Limit refined grains and added sugars.
Conclusion
Both carbohydrates and protein have 4 calories per gram. Following a 2,000-calorie diet, aim to consume 200 to 700 calories --- 50 to 175 grams -- from protein daily and between 900 and 1,300 calories -- 225 to 335 grams -- from carbohydrates. Fats have more than twice as many calories -- 9 calories per gram. Between 500 and 700 calories -- 55 to 78 grams -- should come from fat. Determining the amount of macronutrients you need depends on your individual health concerns; for example, people with compromised kidney function might need to limit protein consumption, because protein digestion burdens their kidneys.
References
- Centers for Disease Control and Prevention: Protein; February 2011
- Medline Plus: Proetin; May 2011
- Centers for Disease Control and Prevention: Carbohydrates; February 2011
- Medline Plus: Carbohydrates; August 2011
- Centers for DIsease Control and Prevention: Dietary Fat; February 2011
- Medline Plus: Dietary Fats; March 2011
Member Comments