16.Carbohydrates, Fats, and Proteins Provide Energy
Carbohydrates, fats (lipids), and proteins are the energy-providing nutrients, because they contain calories.
When we talk about energy, we mean that your body breaks down these nutrients and "burns" them to fuel your activities and internal functioning.
One calorie equals the amount of energy needed to raise the temperature of 1 kilogram (a liter) of water 1 degree Celsius.
Carbohydrates and protein provide 4 calories per gram, and fats provide 9 calories per gram.
The number of calories in a given food can be determined by measuring the weight, in grams, of each of the three nutrients in one serving of the food.
The amount of calories that you need daily to maintain your weight is estimated based on your age, gender, and activity level.
However, you need these nutrients for many reasons beyond their providing energy.
You must consume a healthy combination of carbohydrates, fats, and protein so that excesses, deficiencies, and imbalances don't occur that may increase your risk of chronic diseases.
Carbohydrates supply the simple sugar, called glucose that your cells use as the major energy source to fuel your body. Most of your daily calories should come from carbohydrates.
Fats are another major fuel source. They also help cushion your organs to prevent damage and act as insulation under your skin to help maintain your body temperature.
Proteins can be used as energy, but are better used to build and maintain your tissues, muscles, and organs. You also need protein to make most enzymes and some hormones, to help transport other nutrients, and for a healthy immune system.
A healthy diet should provide adequate amounts of carbohydrates and fats for energy, and enough protein to maintain and repair your body.
Carbohydrates, fats, and proteins are all organic because they contain the element carbon. They also contain two other elements, hydrogen and oxygen. Proteins also contain nitrogen, while carbohydrates and fats do not.