If you don’t want to count calories on a low carb diet, weigh your food. Shellfish is 20 calories per ounce. Fish is 30 calories per ounce. Poultry and pork are 40 calories per ounce. Beef is 60-80 calories per ounce. If you’re eating fish and shellfish, you can eat a pound a day. If you’re eating pork and poulty, you can eat 3/4 of a pound (12 ounces) a day. If you’re eating beef, limit yourself to half a pound (8 ounces) a day.