Serving sizes

Serving size was another definition that may seem obvious at first but is complex to define. Until the Nutrition Facts label appeared, each manufacturer decided for themselves how big a portion was.

• The 1990 US legislation mandated that the serving size should be the amount "customarily consumed and which is expressed in a common household measure that is appropriate to the food"—but knowing what a serving size is required national surveys. 
• In the end, the FDA calculated the US serving sizes by using 139 categories, which includes four types of cereal and four types of cheese.