Retort packs (little silver foil bags) of tuna are available at most grocery stores in the tuna section. If you are not allergic to tuna, but you just hate tuna, you’ll be surprised that you can actually eat tuna in a retort pack. Most people can’t tell the difference between retort pack tuna and white meat chicken. You can substitute a retort pack of tuna for a 3-4 ounce can of tuna on the Cat Food Diet. The only seasoning allowed on the Cat Food Diet is mustard (yellow or Dijon). If you hate mustard, you can substitute Kraft Miracle Whip Free, but only if you don’t like muistard. The amazing thing about the Cat Food Diet is that most patients lose 5-10 pounds a week – and most patients are able to stay on Cat Food for 1-2 weeks. You can also substitute small cans of Vienna Sausage or Spam for your Cat Food of choice,