Are you feeding canned or dry DM?
Once cats are in better BG numbers, they do tend to regain some of the weight they may have lost. When their numbers are high, none of what they are eating is getting into their cells so they lose weight. Insulin helps the breakdown of food into glucose get into the cells so the kitty puts on the weight that's been lost. However, the switch to a low carb diet also can cause a cat to lose weight since it's a species appropriate diet -- cat's are obligate carnivores and don't need carbs. If you're feeding Rico a low carb diet and he's still gaining weight, you will need to slowly reduce the amount you're feeding him.