The Gulp family's Dizzyworld vacation takes a detour when their overburdened RV stops and won't budge. The supersized junk-food junkies - Papa, Mama, Brother, and Sister - are baffled, though slim little sister Dawn, who prefers salads to shakes, declares, "This family's too fat to roll!" Only Dawn appreciates the salad supper offered by kindly Farmer Spratt, but after getting stuck on the county-fair waterslide and experiencing a few similar difficulties, the Gulps realize that they have to get fit to get rolling again. The characters are rabbits humorously outfitted like humans, and the scenes are stuffed with playful details to catch the eye. Wells' message, though couched in silliness and humor, is still obvious; the story may even make some kids feel self-conscious. But in the end, there's no teasing going on; the focus is squarely on the limitations overweight people may experience and the benefits of nutritional eating and activity. A cautionary yet supportive book that highlights an important issue.