Unrefined complex carbohydrates are the best; whole grains, like brown rice are very healthy.
The best carbohydrates are from fresh (preferable organic) vegetables and fruits. They contain many beneficial phytochemicals and fiber. If you are following a low carbohydrate diet, or if you are carbohydrate sensitive, as many overweight people are, grains and rice can cause problems, especially when refined. When digested, all carbohydrates are sugars; problematic with diabetics, hypoglycemics, and with those struggling with weight issues.
Some of the sugar-related side effects can be ameliorated by taking grains in their unrefined forms. The fiber and other nutrients similar to those found in fruits and vegetables can slow down the blood sugar "spike" caused by eating sugar and other unwanted side effects.
