Explain Why Carbohydrates Are Said to Spare Proteins

Fats, carbohydrates and proteins are all integral components of your diet, each playing a role in your body functions. Proteins and carbohydrates, however, play a larger part in energy production. Carbohydrates are said to spare proteins because your body uses carbohydrates for energy instead of proteins, according to Richard Stockton College Athletic Training. As a result, your body uses proteins for other purposes, such as rebuilding muscles, making enzymes or producing antibodies. Understanding how proteins and carbohydrates work together can ensure that you have enough energy, especially for athletic performance.

Using Carbohydrates

Carbohydrates break down into glucose in your body. Glucose is your cell’s energy source -- think of this process as similar to putting fuel in your car's gas tank. Your body can store carbohydrates in your muscles and liver for later use, but only to a certain extent. For example, when you engage in athletic activities, your body starts using stored carbohydrates as an energy source. If you burn through these stored carbohydrates, your body will no longer spare proteins as an energy source.

Using Proteins

Carbohydrates are stored as energy in your muscles in the form of glycogen. Your body will release glycogen to provide you with energy when you do not have enough glucose circulating in your blood. If your glycogen levels become too low, your body will signal your muscles to release protein from your tissues, which can deplete lean muscle from your body. To counter this, you need to consume enough carbohydrates so that proteins will be spared from being released as an energy source.

Side Effects

When your body is forced to use proteins for energy, the loss of lean muscle tissue can make you feel weakened, according to Iowa State University Extension. Also, your kidneys must work overtime to excrete the waste products from the protein breakdown in your urine. Because your body uses carbohydrates exclusively as an energy source, the depletion of carbohydrates and subsequent use of proteins can lead to adverse mental symptoms, such as dizziness, weakness and decreased mental performance.


Consuming enough carbohydrates and proteins is vital to keeping your body working at its best. Consuming a no-carb to low-carb diet or not refueling during or after athletic performance means that carbohydrates will no longer spare proteins. If you are an athlete or you exercise regularly several days a week, you’ll need roughly 3 to 4 grams of carbohydrates for every pound of your body weight, according to Richard Stockton College Athletic Training. If you are a physically active adult, you will need to consume about 1.0 gram per kilogram of your body weight per day, according to Montana State University. By maintaining regular intakes of both carbs and protein, you will give your body enough energy sources for fuel.