What does our body do with the glucose from a meal?
Insulin directs muscle, fat and the liver to use glucose, fructose and galactose as the primary fuel. This allows for a lot of carbohydrate entering the body from a meal to be used for energy immediately. In addition, insulin directs muscle and liver, and to a lesser extent other tissue an as well as to store extra carbohydrate as glycogen. Glycogen is composed of large branching links of glucose and is very similar to plant starch. However, only so much glycogen can be made since glycogen is meant to be a short term not a long term energy reserve.
How much glycogen is in our body?
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Our liver can generate up to 6 to 8 percent of its weight as glycogen for about 75 to100 grams total. Meanwhile, only about 1 percent of the weight of skeletal muscle cells is attributable to glycogen. However, since the total amount of skeletal muscle in our body far exceeds our liver, muscle will contribute much more to our total glycogen stores. Skeletal muscle may contain about 250 to 400 grams, which is about four-fifths of our total glycogen stores. Since carbohydrate provides 4 calories per gram the potential energy from glycogen is typically 1400 to 2000 calories, not very much. As you may expect, people with more muscle resulting from exercise training will have more body glycogen due to increased muscle mass. In addition, their muscle will adapt to hold double and even triple the amount of glycogen it can store. |
Interestingly, even though carbohydrates contribute approximately one-half of the energy in our diet, our body composition is not reflective. That’s because only 1% or less of our body weight is comprised of carbohydrate. This means that carbohydrate is stored with limitations, most of which is in our liver and skeletal muscle as glycogen. Other tissues, such as fat cells and the heart, contain a little glycogen as well; however, the contribution to our total body glycogen stores is very small. Since glycogen stores are relatively small there must be another means of storing the excessive energy from diet derived carbohydrate.
Can carbohydrate from our diet become body fat?
Since the potential to store carbohydrate as glycogen is somewhat limited, we need another means of storing excessive diet carbohydrate energy. As our liver and skeletal muscle is busy making glycogen, our liver and fat tissue will also begin to convert some of the extra glucose to fat. The fat that is made in our fat cells is stored within those cells. Meanwhile, the fat that is made in the liver is transported in the blood to fat cells and to a lesser degree other tissue such as muscle, breast tissue, etc.
Interestingly, scientists have determined that our ability to convert excessive carbohydrate to fat might not be as efficient under normal conditions as we once thought. It now seems that consuming excessive carbohydrate diet can increase the level of body fat by decreasing our use of fat as a daily energy source. That’s because our body is forced to use more carbohydrate as promoted by insulin. This situation tends to happen more when people eat too many calories and have type 2 diabetes (or prediabetes).
