Carbohydrates or sugar, in their simplest forms, give us energy. We need carbs in our diets. However, if we eat too many carbs or too much added sugar, our bodies become less able to manage high blood sugar levels. Over time, this can cause damage to our eyes, kidneys, heart and other organs. Excess sugars are also stored as fat. Diets high in sugar have been linked with higher risks of heart disease, diabetes and obesity, according to a 2014 study in the Journal of the American Medical Association.