The energy or calories in the food we eat comes from three macronutrients: proteins, fats, and carbohydrates. Macro means large, and these basic nutrients are necessary in large quantities to sustain our growth, metabolism, and other bodily functions. Our bodies require other nutrients, too, like essential vitamins and minerals. However, these micronutrients are required in smaller quantities. While critical to our health, micronutrients do not provide us with energy.
Macronutrient #1: Protein (4 calories/gram used to build and repair our body)
Protein is the main component of our organs, muscles, all our living cells, and almost all our body fluids. Proteins are chains of amino acids linked together. There are 20 different amino acids, and all of them must be present in order for our bodies to build, maintain, and repair themselves. Nine of these 20 amino acids are deemed essential because they can’t be manufactured by our body; they must come from the food we eat.
Proteins that contain all of the 20 amino acids are called complete proteins. They can be found in animal sources: meat (poultry, fish and other meats) and dairy (eggs and milk products). Proteins that come from plant sources are considered incomplete because they do not contain all 20 amino acids, However, you can combine different plant sources to obtain all of the amino acids you need.
You don’t need to eat animals in order to supply your body with adequate protein. In fact, if you compare meat and dairy to dark green vegetables, soybeans, and other plant sources, you will find that the plant foods often contain more protein — based on an equal number of calories — than their animal counterparts.
Macronutrient #2: Fat (9 calories/gram used as a fuel source)
Fat is also necessary to maintain a healthy body. It’s vitally important for building body tissue and cells, and it aids in the absorption of some vitamins and other nutrients. Just like there are essential amino acids, there are also essential fatty acids which must come from food. Many people eat too much of the bad fats, but also eat too little of the good fats required for optimal health.
It’s not just the fat we eat that can become fat on our bodies. Any macronutrient not immediately needed by our bodies is stored in our energy reserve as excess body fat. When needed, it can be broken down and used for energy but all too often ,it just sits there collecting more fat.
Macronutrient#3: Carbohydrates (5 calories/gram used as a fuel source)
Carbohydrates are chains of simple sugars and are the body’s main source of fuel. They are broken down and enter the bloodstream as glucose. Excess glucose is stored in the form of glycogen in the liver and, in limited quantities, the muscles.
Simple carbohydrates can be metabolized quickly and therefore provide the quickest source of energy. They include the various forms of sugar, such as sucrose (table sugar), fructose (fruit sugar), lactose (dairy sugar), and glucose (blood sugar).
Complex carbohydrates take longer for your body to metabolize them to provide energy. They include starch, glycogen, and cellulose, and are found in vegetables and unrefined whole grains. Complex carbohydrates are also excellent sources of fiber.
Fiber is a form of carbohydrate that our bodies cannot digest. It is not only important for health, but is a significant factor in weight loss.