What Are the Main Energy Sources in Food?

Your body gets energy from what you eat. Calories, also known as kilocalories and food calories, are the units of measurement for dietary energy. Balancing the calories you consume with the calories you expend, or burn, lets you maintain your weight. You can lose weight if you expend more calories than you consume. Choose a balance of carbohydrates, protein and fat from nutritious foods to meet your nutrient requirements while staying within your calorie limit.

nuts are a source of both protein and healthy fats (Image: Svetl/iStock/Getty Images)

Carbohydrates

oatmeal is a nutrient-dense high-carb food (Image: oksix/iStock/Getty Images)

Carbohydrates provide 4 calories per gram, and they are the primary source of energy for the body. According to the Dietary Guidelines for Americans 2010, carbohydrates should provide 45 to 65 percent of your total calories, which means you should get 225 to 325 grams of carbohydrates per day on a 2,000-calorie diet. Nutrient-dense high-carb foods include whole grains, such as whole-wheat bread, oatmeal and barley; and legumes, or beans, peas and lentils. Low-fat milk and dairy products, fruit, and starchy vegetables, such as sweet potatoes, also contain carbohydrates. Sugary foods and refined grains, such as white bread, are high in carbohydrates, but they are less nutritious.

Protein

fish is an excellent source of protein (Image: igorr1/iStock/Getty Images)

Protein's primary role is to maintain lean muscle mass and help with tissue repair and healing. Protein can be a source of dietary energy if adequate calories are not consumed or if protein is consumed in excess beyond muscle and tissue needs. Protein may also reduce hunger and help you control your weight. Healthy adults should get 10 to 35 percent of calories from protein, according to the 2010 Dietary Guidelines. Each gram of protein provides 4 calories, so a 2,000-calorie diet should include 50 to 175 grams of protein per day. Sources include meat, poultry, seafood, eggs, beans, dairy products, nuts and peanuts. Whole grains and vegetables also provide small amounts of protein.

Fat

butter is high in saturated fat (Image: tycoon751/iStock/Getty Images)

Each gram of fat has 9 calories, which is a little more than double the amount of carbohydrates and protein. Healthy adults should get 20 to 35 percent of calories from fat, or 22 to 77 grams of fat per day, according to the 2010 Dietary Guidelines. Most of your dietary fats should be unsaturated to reduce your risk of heart disease. Sources include nuts and peanuts, seeds, vegetable oils and fatty fish. Butter, fatty meats and full-fat dairy products are high in fat, but it's unhealthy saturated fat, which can raise your cholesterol levels and increase your risk for heart disease.

Alcohol

both men and women should limit alcohol consumption (Image: Boarding1Now/iStock/Getty Images)

Alcohol is another source of energy, providing 7 calories per gram, but the 2010 Dietary Guidelines caution that most sources of alcohol do not provide essential nutrients. Alcoholic beverages are the fifth highest calorie source for the average American adult. Some alcoholic beverages may come with health benefits, though. Red wine, for example, can raise levels of healthy HDL cholesterol, according to an article published in the "Polish Heart Journal" in 2013. Men should have no more than two alcoholic drinks per day, and women should limit consumption to one drink per day.