Because only the smallest molecules of sugar can pass through the intestinal walls and into the blood stream, foods ingested as simple carbohydrates (single- and double-molecule sugars) can be used immediately while complex carbohydrates (three or more molecules) require more time and action to break down and be absorbed. Think of carbohydrates entering the gastrointestinal tract like pieces of wood going into a chipper. Simple carbs, much like narrow branches and leaves, are quickly and handily minced — they are no sooner in the mouth of the chipper than they are ground down and hashed. Disaccharides are broken down into monosaccharides in the small intestine. From there, simple sugars pass easily into the bloodstream and then to cell membranes to be burned up. Complex or “long chain” carbs are bigger pieces, like thick branches and tree trunks that have to be fed slowly through the chipper to be broken down. Due to their bulkier, compound structure, complex carbs remain in the system for a longer time, providing slow-burning energy and longer durations of satiety, or feeling full.