First, congrats on getting such a good vet! That is fabulous. There aren't enough like him or her.
I understand your pain. It took me 2 weeks to get my girls converted. I wasted food and money. But it was so worth it! Poppy lost 5 pounds the first year, and I didn't have to starve her.
Anyway, you can start by cutting back only slighly on the regular food. That way you'll know that kitty is still getting enough to eat, but not so much that he won't be hungry enough to try something new.
Keep doing what you're doing - but perhaps just put out a spoonful of the canned food at a time to cut back on waste. At some point he may realize that it's food and acceptable to eat.
You can also try crushing some kibble to sprinkle over the top. That might work better than whole kibble bits. You can also try nuking the food just for a few seconds to bring out the scent.
You can try other bribes such as liver or fish flakes, or even a bit of tuna or tuna water. Or maybe try fishy cat foods. It's the nose that brings them in, so that might work.
And keep trying different brands and flavors. You will eventually find one that will entice him to eat.
Every cat is different, of course, but I found that Natural Balance venison & green pea is what finally got Poppy eating. Perhaps it's extra succulent or something!
So don't give up. Your cat will lose weight and will be so much healthier if you persist!
FROM MY BLOG:
In a nutshell, most cats are fat because they've been fed too much (free-feeding or indulging them) and because they're fed dry food which is NOT appropriate food for them due to the grain/carb/sugar content. Cats are obligate carnivores who need to eat a high meat-based protein diet, which is also high in fats and low in carbs.
Many vets, who are sadly ignorant on the topic of proper cat nutrition, will recommend prescription diet foods (usually dry). Cats are expected to lose weight on a starvation diet of 1/4 or 1/3 cup of food per day. Everyone is miserable in these situations.
The solution is to switch the fat cat (and any others in the household as well) to a good quality canned food. Because these foods are species appropriate, the cat will lose weight at a safe, slow pace (no more than 1 pound per month). Switching foods needs to occur slowly, and if you're trying to get a kibble junkie to eat canned food, that will happen naturally.
How much should cats eat?
This varies. Average cats may eat between 20-30 calories per pound per day. But note that that is IDEAL pounds. Using 25 calories per day for example, an 8 pound cat could eat 200 calories per day. By the same token, a cat who weighs 20 pounds but should weigh 10 could eat 250 calories per day. You multiply the ideal weight by the calories to arrive at that figure. When working toward weight loss, it's perhaps best to start at the lower end of the scale (20).
How do I find out how many calories are in cat food? See the link "Values in canned food." If it's not listed there, you'd need to contact the manufacturer.....I believe that link provides some help there as well.
That's it. Easy as pie. Not only will fat cats lose weight, but it and any others in the home will reap many benefits of eating a speciies appropriate diet.
See the links below for detailed information on this topic.
UPDATE: Poppy lost 5 pounds and Sophie lost 2 following this plan (from October to October). Each cat gets one can (5.5oz) of Nature's Variety Instincts per day. No one is starving or miserable. My vet is happy with her progress and so am I. Only 4 pounds to go!