Hi Jennifer and Squeak and welcome to the forum

It depends on the size of the cans you are feeding. A normal well cat of 11 lbs would probably eat about 3 small cans a day.
Cats diagnosed with diabetes have often lost weight when they are diagnosed. This is because their bodies are unable to absorb all the nutrients. Once their diabetes is under more control and the blood sugars are closer to normal, they will start to put on weight. He will need more food while he is unable to absorb all the nutrients, so if he is hungry or still losing weight, feed him more.
Are you feeding low carb, under 10% food. No dry food.
Are you giving the insulin twice a day.?
What type of insulin is he having?
If he is still losing weight give him more food. You can also feed him during the day as well as before the insulin shot.
The best thing you can do for your kitty is to home test the blood sugars. It doesn't hurt the cat and you will be able to keep Squeak safe. Here is a link to testing.
http://www.felinediabetes.com/FDMB/threads/hometesting-links-and-tips.287/
If you live in the US, Walmart has Relion human glucose meters to test the cats blood.
If you would like more information on how to help your kitty, post over on the main forum where there are many people who can help and support you. Here is the link
http://www.felinediabetes.com/FDMB/forums/feline-health-the-main-forum.28/
Hope to see you again soon.
