A meal containing mainly complex carbohydrates is likely to give you more energy and leave you feeling fuller than a meal containing mainly simple carbohydrates, according to a study published in the "International Journal of Obesity and Related Metabolic Disorders" in June 2003. Of the three types of carbohydrates, two -- starch and fiber -- are considered complex carbs, while the other -- sugar -- is considered a simple carb because it is very quickly digested and absorbed. Starch and fiber take longer to pass through the digestive tract because of their more complex structure.
Classifying Your Carbs
Milk, fruits and some vegetables contain naturally occurring simple carbs, but the foods are still healthy because they are rich in other nutrients such as vitamins, minerals, fiber and phytonutrients. The simple carbs you need to limit are added sugars, such as those found in desserts, candy, soda and sugary cereals, according to the American Heart Association, since these provide calories without nutrients. Complex carbs are found in fruits, vegetables, whole grains, nuts and beans and other legumes.