Carbohydrates (sometimes called saccharides by scientists, and “carbs” by everyone else) are a rich source of energy for both people and animals.
There are two kinds of carbohydrates. Simple carbohydrates are monosaccharides, and are found in abundance in many fruits and dairy products, as well as processed food like white bread, pasta, and every product that contains white sugar—cakes, ice cream, chocolate.
Complex carbohydrates or polysaccharides are found in vegetables (in the cellulose), whole grain bread and pasta, legumes, and food with unrefined grains (such as brown rice and oatmeal).
Simple carbohydrates are quite easy to digest and release energy quickly, explaining the sudden “rush” people may feel after having a chocolate bar. Complex carbohydrates on the other hand take longer to digest so release energy slowly over a longer period of time. Thus, even a bowl of oatmeal will fill the stomach for several hours, while the same sized bowl of fruit will lead to hunger pangs by the middle of the morning.
The sugars in carbohydrates are broken down by the liver into glucose, which triggers insulin production in the pancreas. Simple carbohydrates lead to a sharp spike in insulin levels while complex carbohydrates lead to lower levels of insulin. People who have a high level of sugar may develop Type Two Diabetes and must monitor their insulin or sugar levels.
The body needs glucose for energy. However if the body has too much glucose and too little exercise (and low energy requirements) the excess glucose will be converted into fat. The fat can only be burned after long periods of exercise.