Can fast food be part of a healthy-eating plan? Sure, if you order wisely and choose fast food only occasionally. If the fast-food restaurant offers several sandwich sizes, pick the smallest. Bypass hamburgers with two or three beef patties, which can pack more than 800 calories. Instead, choose a regular- or children's-sized hamburger, which has about 250 calories. Also, skip the large serving of french fries and ask for a small serving instead. This switch alone saves 200 calories.