The Filet-O-Fish is one of McDonald's most popular menu items. The Filet-O-Fish sandwich contains 340 calories, 17 grams of fat, and 11 grams of protein. It also contains 20 grams of carbohydrates, 3 of which are from fiber. So, overall, the Filet-O-Fish is not Fully healthy. If you're looking for a healthier sandwich at McDonald's, you might want to try the grilled chicken sandwich or the Artisan Grilled Chicken Sandwich.