Carbohydrates (car-buh-HIGH-druts) are the starches and sugars in the diet that are used by the body primarily to supply energy. Carbohydrates is considered an 'essential nutrient,' asubstance the body is unable to make on its own, so it must be obtained from food. Carbohydrates have four calories per gram. 'Complex' carbohydrates are starches in their natural, unrefined form, such as whole grains, beans, vegetables, and fruits. 'Simple' carbohydrates include such things as alcohol, honey, sugar, and corn syrup, which are 'empty' calories, calories without any nutritional value, fiber, or bulk. Complex carbohydrates are more filling than simple ones and biochemically signal your brain that you've had enough to eat. They're also higher in fiber and lower in calories and are hard for the body to convert to body fat, which keeps you slimmer. It also takes more calories for your body to digest and metabolize complexcarbohydrates than it does to digest and metabolize simple sugars, which means you can eat more complex carbohydrates and put on less weight than when you eat other types of foods.