Another advantage of a fish and shellfish diet is the built in portion control. Restaurants seldom serve more than 12 ounce portions of fish, while you can often readily get a pound and a half of steak or more. Lobster tails are generally limited to 5 or 6 ounces, 9-10 ounces is about the max. Canned tuna and salmon are portion controlled with the calories on the label. And it’s almost impossible for most people to eat more than 2 pounds of shrimp at a sitting, it’s just too much food.