Plants create carbohydrates during photosynthesis, and while the initial product of photosynthesis is glucose, plants store carbohydrates as one of several saccharides. The human body stores carbohydrates that it does not use quickly. While it stores some of this energy in the liver and muscles in the form of glycogen, it stores the rest as fat. According to About.com, the body is able to live without dietary carbohydrates if needed.
WebMD divides carbohydrates into several groups. In the human diet, a serving has approximately 15 grams of carbohydrates. In addition to plant sources, dairy products are often a hidden source of carbohydrates. Refined sugars, like those in sweets, often provide a very condensed source of carbohydrates. The exact number of carbohydrates per serving in sweets varies according to the ingredients in the recipe.
Sugars, starches and fiber are the main types of carbohydrates. The Mayo Clinic says, "Terms such as 'low carb' or 'net carbs' often appear on product labels, but the Food and Drug Administration does not regulate these terms, so there's no standard meaning." A food's glycemic index classifies it according to its potential to raise blood sugar levels. Several weight-loss diets base their eating plans on the glycemic index and recommend avoiding foods, such as snack foods, potatoes and corn, that are high on the index, while including foods like whole grains that rate lower.