Group activity for nutrition and weight control?

[blessedmommy]

I am leading a group about nutrition and weight control in a couple of weeks. I am needing an activity that is appropriate for adults that can also be used as a teaching tool about nutrition and weight control. I am having a hard time coming up with something that isn't too kiddish. The activity needs to be about 10 minutes long or under, and must be something everyone in the group can do. It can be as simple or elaborate as it needs to be as long as it gets the point across. If anyone has any ideas please let me know. Thanks