The unique Diet jams contain 30% fewer calories than regular jams. They are 100% natural and sweetened with fruit sugar fructose. Jam typically contains both the juice and flesh of a fruit or vegetable, although some cookbooks define it as a cooked and jelled puree. The term jam refers to a product made of whole fruit cut into pieces or crushed, then heated with water and sugar to activate its pectin before being put into containers.