Carbohydrates are categorized as simple or complex sugars and occur naturally in many healthy foods: grains, fruits, starchy veggies, nuts, seeds and legumes. Generally speaking, complex carbs are digested more slowly and have a smaller effect on blood sugar. They also offer healthy fiber! On the other hand, processed or refined carbs contain many simple sugars that are quickly absorbed into the bloodstream and can lead to weight gain, diabetes or cause other health issues.