If you drink a soft drink containing 33 grams of sugar (sucrose) why don't you gain the weight of the sugar? If the sugar enters into catabolic pathways the sugar will produce CO₂ by aerobic respiration. If the sucrose is completely oxidized (catabolized) the atoms of C and atoms of O from sucrose will be excreted as CO₂. The H mass found in the sucrose molecules will unite with O₂ (ultimately from breathing) to produce water. Some of the water will be eliminated by breathing, some by urine, and some may be kept. If the sugar is not needed for cell respiration, then the sugar will be converted to polymeric storage molecules such as glycogen and lipids. For glycogen synthesis to occur the sucrose is converted to glucose-6-P and then coverted to glycogen. For lipid synthesis from sucrose to occur, the sucrose is coverted to glucose-6-P, catabolized to acetyl CoA and then undergoes lipid synthesis. In an anabolic state the individual ingesting 33 grams sucrose will retain a higher proportion of the mass. There will never be 100% weight gain owing to the fact that the body will distribute the 33 grams into both catabolic and anabolic pathways.