“We spoke with our vet, who recommended against our current feeding regimen; saying it may be too small of a portion, causing him to go into starvation mode.”
Your Vet is 1000% correct. When the body is deprived of food, the thyroid gland will slow down the metabolism, causing the animal to not only gain weight, but to make weight loss very, very difficult. It’s why recovering anorexics often have hypothyroidism, and why people with hypothyroidism have problems with their weight stagnating even when they barely eat and get plenty of exercise. In fact, if the dog does have a thyroid problem, increasing exercise at this point might make weight loss impossible.
Consider this: when I was a teenager, I knew someone who fed a 40lb dog *one* 6oz can of Mighty Dog daily. The owner’s reasoning being that was the ration her last dog received, never mind he was a 20-ish lb lhasa mix. Needless to say, she wasn’t the brightest spark. However, despite both her dogs being underfed, they were actually overweight; the larger one at one point grossly so, despite the fact the she was being outright starved.
Offhand, I’d say for a 75lb inactive dog, no less than 2-2.5 cups per day should be fed. Just to give you a better idea of how low the amount you’re feeding is for a dog that weight, my 30lb Beagles get slightly less than 1.5 cups daily, and my 25-ish lb Beagle pup gets that or slightly more. When I had my 65lb Shepherd mix who hardly ate anything to keep a healthy weight would get no less than 2 cups. My purebred GSD was the same weight as the mutt, but had a higher nutrient requirement, and normally ate around 3.5-4 cups daily. Both were lean dogs, with not an ounce of spare fat.
For what my humble advice is worth, I would suggest taking this dog off Wellness altogether. Of all the feeds I’ve tried over the years, it was one of the absolute worst. Think I had somewhere around 13 adult dogs and a litter of pups on both the original grain inclusive formula, CORE, and Small Breed Puppy – and not a single one of them did well on it. Coats went to pot, problems with hypoglycemia and loose stools, etc.
Look for a feed that has a relatively low kcal content, so that you can feed this dog more food without giving an excess of calories. Aim for something around 340 kcals per cup or less, with moderate amounts of protein and fat. Be VERY careful with those grain free fad diets, because they often contain an unhealthy excess of protein and other nutrients. Or are made more with the owner’s sensibilities in mind than what the dog actually needs. And if it comes down to a prescription diet, that’s a far better alternative to the health problems being overweight will cause.
