The actual diet plate comes in 2 sizes - men and women!! The manufacturer reckons you can pile it up as high as you can until the food spills over into the next boundary. The portions in my opinion are ok - satisfactory. Not sure whether the bowl comes in different sizes though?
The bowl (for anyone who's interested) has rings around the inside which guide your cereal portion depending on the type of cereal you have i.e. museli is a very small circle, sweet cereal like frosties etc are obviously smaller portions than say special K etc