Carbohydrates are foods that are rich in sugars or complexes of sugars. Depending on how these sugars are arranged, we call a food either a source of simple or complex carbohydrates. Fruits and sugars are simple carbohydrates because they contain easily-digested sugars. When sugars are bound more closely in foods such as starches (whole grains and legumes, for example), they are called complex carbohydrates. It takes the body much longer to digest the sugar from a complex carbohydrate.

Simple carbohydrates include sugar, high fructose corn syrup, white flour, white rice, etc. These are foods that have had the fiber and bran removed through processing, leading to quick absorption and causing blood sugar to rise too high. This in turn is converted to fat. Worse still, large amounts of these simple carbohydrates can be consumed without us becoming full, leading to even more fat formation.

Fruit sugars are simple carbohydrates, because the fiber and the bran has been removed. However, fruit in its whole form is rich in fiber and is therefore beneficial.

Most of the benefits attributed to carbohydrate foods come from the slower-digesting, complex variety. Complex carbohydrates are, in general, better because they take longer to digest. The sugars in these foods enter the body more slowly. They do not cause the sharp spike in blood sugar that can be caused by simple carbohydrates -- especially sugars such as white sugar, honey, and other concentrated sweeteners.

Complex carbohydrates include whole-wheat flour, brown rice, fruits, vegetables, grains, and beans in their natural forms. Carbohydrate foods in their natural state have many benefits: They are high in fiber, low in fat, and a good source of vitamins. They can also be a good source of minerals, depending on the mineral content of the soil they were grown in.

Complex carbohydrates, being rich in fiber, provide a double benefit to your diet. First, the fiber fills you up before you get too many calories -- you feel full, and therefore stop eating. Second, fiber slows the absorption of food, so your blood sugar rises slowly, preventing an exaggerated insulin response.

When people talk about reducing carbohydrates in the diet, they are referring in almost all cases to simple carbohydrates ("refined carbohydrates"), not complex carbohydrates.

The most healthful and scientifically proven approach is to switch from simple carbohydrates to complex carbohydrates. As a general rule, this means avoiding refined foods: brown rice instead of white; whole wheat bread instead of white bread; products with added sugar and so on.