Weight gain as done by an ME dog owner: Not to be tried as is without thorough discussion with your veterinarian.

I am very glad to hear xxxxxx is doing much better. If his stomach is anywhere as sensitive as it sounds, PLEASE approach adding calories with extreme care. And it seems just a bit soon to be doing it, as well.

I would strongly suggest you consider the following:
1. Start adding calories by adding something to the I/D, like powdered oat bran. It has 150 calories in 1/3 cup and you can probably pack that much or close to it into a single can of I/D. Whatever you do — test a very small amount first and build up. Either add just a little to all the balls, or add some to just a few. Don’t do it all at once. If the oat bran dries the exterior of the balls, roll them in olive oil before feeding. Powdered oatmeal works too, but avoid instant, it’s harder on the stomach.
2. If you are feeding knox blocks with your balls, try using coconut milk. It’s got fat, but unsaturated. Again, just a few at first. And this is not the first thing I’d try.
3. If you are going to switch to a new canned food, do it ever so slowly…and plan to keep the I/D as some portion of his food for quite a while. Don’t expect to phase it out in 4-5 days like it says on dog food websites.

If he was eating Natural Balance LID Venison & Sweet Potato with Crude Fat 4% and calories 400 per can, it doesn’t get much better than this considering a calorie to fat ratio. This food is below average fat and below average protein, which is what you want. And 400 calories per can is more than you get with most low fat dog foods. Limited Ingredient is a good idea unless you know precisely what sets his stomach off. I have spent dozens of hours trying to solve the same problem for my dog, who gets acid reflux from absolutely everything. But she tolerates pureed food so we’re going to try the Honest Kitchen once she’s off the bland diet for the third time in as many months…I would stay away from anything lamb! too much fat.

WHATEVER YOU DO, INTRODUCE ONLY ONE CHANGE AT A TIME OVER SEVERAL DAYS.

I think you had one of the most likely to work foods for your situation, but if you are SURE it was the Natural Balance LID Venison and Sweet Potato that caused the reflux, I wouldn’t go above 5% crude fat with your new food … and given your limitations, you may not be able to use a food with the perfect consistency. You may have to firm it up with powdered oat bran or oat meal or something. I have seen only two canned foods mentioned here for having the ‘perfect’ consistency for meatballs: Wellness Complete Health Venison and Sweet Potato, and an unspecified variety of Natural Balance (cannot be Ultra original – I’ve used that and it’s terribly watery).

You may find info at the link below helpful, specifically I’ve copied for hypoallergenic / food intolerance recommended foods.
http://www.dogfoodadvisor.com/best-dog-foods/hypoallergenic-dog-foods/

Great advise. I just have one thing to comment on regarding the “hypoallergenic” foods that are suggested in the Foster and Smith article: they may be “limited ingredient” diets, but, they are not actually “hypoallergenic” diets; ie. they still contain ingredients to which dogs can commonly be allergic to. It may be splitting hairs, but, when we see a patient who we think may have food allergies or intolerances and we advise a hypoallergenic diet, it needs to be one without ingredients that the pet has never been exposed to, ero the prescription hypoallergenic diets.

As long as a pet owner realizes that the over-the-counter (OTC)catalog diets are not truly good test diets, we’re all on the same page. when we see a patient and suggest a hypoallergenic diet, owners will frequently say that they’ve already been tried. Then we have to explain the difference. It is not WRONG to try the limited ingredient diets, just realizing that they may not be as effective. this is part of the ART of practice.