There isn't any secret there...it is just simple healthy "whole" foods-fruits, veggies, lean meats, skim dairy, and choosing whole grain carbs like whole wheat pasta and oatmeal over simple carbs. (white bread, bagels, 80% of cereals, and all the refined stuff like cookies, cakes, crackers, etc.) High in produce and fiber, and lean protein.
They do nothing special to "trim the ab area" alone...eating this way is a very healthy way to eat and if you eat this way and reduce your calorie intake-you will lose all over-not just the abs. It is just because the abs are the "In" body part the past few years.