A Reasonable Portion Control Test?

Palm of the hand test helps control weight -- this article is for kids, but I like the idea - Adults could use this or some variation of this for easy portion-control testing too. Obviously it wouldn't always work, for example, a salad that would only fit in your hand would not be very filling at all. But, for full-calorie dishes it makes sense to have some sort of a constant, always-with-you measurement.