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 and 40 grams of fat. Instead, choose a regular- or children's-sized hamburger, which has about 250 to 300 calories. Also, skip the large serving of french fries or onion rings and ask for a small serving instead. This switch alone saves 200 to 300 calories.