The three major sources of calories are carbohydrates, protein, and fat. Some foods, such as fruits and vegetables, easily fit into one category (carbohydrates. Other foods, such as meat, obtain their calories from more than one category (protein and fat). For simplicity, we place these foods into the category that supplies the most calories. For instance, meat is classified as a protein because the protein in meat accounts for the largest number of calories.
Carbohydrates.
The first major source of calories is carbohydrates. Carbohydrate are found in fruits, vegetables, and grains. Foods in this category contain about four calories per gram. For good nutrition, carbohydrates should account for approximately 50-60% of your daily caloric intake.
There are two types of carbohydrates: simple carbohydrates and complex carbohydrates. Simple carbohydrates include refined products such as table sugar and candy. These carbohydrates do not offer the nutritional benefits of complex carbohydrates and should be limited in your diet. Complex carbohydrates offer many vitamins, minerals, and fiber and are found in unrefined grain products, vegetables, and fruits. .
Protein.
The second major source of calories is protein. Protein is found in meat, fish, poultry, legumes, dairy products, and eggs. Protein is essential for the growth and maintenance of human cells. Foods in the protein category contain four calories per gram. Studies show that protein should supply approximately 12-20% of your daily caloric intake. .
Although protein is found in both animals and plants, only animal sources of protein contain amino acids, which the human body needs for good nutrition. However, animal sources also contain fat. Nutritionists warn that too much fat can be harmful and recommend limiting the consumption of animal protein. Besides providing protein, plant sources contain no cholesterol and are a good source of fiber.
Fat.
The third major source of calories is fat.