Maltodextrin, also known as multidextrose or glucose polymer powder, is a synthetic polysaccharide, i.e. a complex carbohydrate. It is used by a range of sports people to help meet the high-energy demands of intense exercise, especially by tri-athletes. Although structurally it is a complex carbohydrate the chemical structure is such that it is open to rapid enzymatic degradation, i.e. it is digested and absorbed very rapidly, infact faster than sugar, so it scores high on the glyceamic index. For this reason many people are worries it will put on fat so in bodybuilding it is invaluable for the lean hard gainer who struggles to eat enough carbohydrate each day. By adding the powder to drinks can increase intake by 6-800kcals a day. It is also useful for post workout replenishment of carbohydrate stores. Maltodextrin powders are cheap, and useful for bulking up on.
btw, I'm still shaking my fist at you.