Is the bright yellow coating inside the bag cause for concern? Yes. Much of it is saturated and trans fats. But while many microwave popcorns, especially those with extra butter, contain a significant amount of bad fats, there’s an increasing number of reduced-fat choices, says Elaine Magee, a registered dietitian in California’s Bay Area. “An occasional splurge on the extra-butter varieties is OK,” she says, “but avoid eating them frequently.”