Carbohydrates are the body's preferred energy source. The carbohydrates you eat provide energy to your muscles, brain and nervous system; facilitate the metabolism of fat; and ensure that the protein in your muscles is not broken down to supply energy. Because carbohydrates are so important to your bodily functions, any excess carbs you eat are stored in your liver, muscles and fat for future use.
How Carbohydrates Are Stored
When you eat carbohydrates, they are broken down into small sugar molecules in your stomach. These molecules are transported through your digestive system and then converted into glucose by the liver to make a usable form of energy for the brain and your muscles. Carbohydrates are stored in the body in the form of glucose or glycogen.
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When Glucose Is Stored
Any glucose that is not needed immediately for energy is converted into glycogen and stored, according to a 2016 ScienceDirect article. Your body can store around 2,000 calories' worth of glycogen, which can be used when you need more energy than is currently available in your bloodstream.
How Glucose Is Stored
Insulin is a hormone secreted by your pancreas when your blood sugar levels are too high. According to an article published in the Encyclopaedia Britannica, insulin interacts with your liver, muscle and fat cells, telling them to accept incoming glucose.
If you don't have enough insulin or if the insulin in your bloodstream doesn't work as it should, you develop a condition called diabetes in which you can't regulate your blood sugar levels.
Loading Up the Liver
Your liver stores the most concentrated amount of glycogen of all the storage sites in your body. It can hold up to about 100 grams of glycogen at any given time. This glycogen is primarily used to maintain blood sugar and energy levels throughout the day.
Massing in the Muscles
Your muscles account for 20 to 30 percent of your total mass and therefore provide storage for a larger total amount of glycogen than the liver does. A healthy, well-nourished adult may have about 500 grams of muscle glycogen. Your muscles are the secondary storage facility, filling up only when the liver has reached its storage capacity. Muscle glycogen is used for energy during prolonged strenuous activity. Your muscles and liver together can store around 600 grams of total carbohydrate as glycogen.
How Excess Glucose Is Stored
If your intake exceeds the amount required to fill your liver and muscle tissue, your liver will convert the excess carbohydrate into glucose and release it into the bloodstream. At this point, insulin released from the pancreas will signal your fat cells to take up the excess glucose and store it for future use.
Use of Carbohydrates
Stored-up glycogen is used for energy in the body. Carbohydrates are stored as glycogen in muscles, and they use it to power contractions during exercise. Your brain uses the glucose that floats around your bloodstream to power electrical signals.
Your Brain on Glucose
It's estimated that the brain consumes about 20 percent of your body's total energy, according to a 2013 study published in Trends in Neuroscience. This is astonishing, considering it takes up only around 2 percent of your body weight.