Sugar can affect the weight and volume of food. The volume of liquid is only affected slightly by sugar. The volumes of bakery products can be affected in various ways.
Sugar increases the volume of bread because the yeast breaks down all or partof the sugar/syrup and transforms it into various components, including carbon dioxide. This carbon dioxide increases the volume of the bread and makes it more porous.
In sponge cakes and cup cakes sugar creates bulk – in other words volume. The sugar still has a physical presence. If we were to stop using sugar in these products the amount of energy obtained from fat would increase.