Small breed dogs, like your Papillon, Phalene are easily over- pampered, spoiled, by giving him too many snacks, goodies, and leaving his food all day out for him to nibble on.
So, you ended up with an overweight Papi, or even obese Papillon.
If you are not sure, test, by stroking along the sides of his body. Do you fee his ribs? If you have troubles to feel his ribs, then your dog is at least plump.
Plump, fat, overweight, obese dogs are just as unhealthy as people are in that situation; leading to kidney problems, heart disease, you name it.
And like in people, the main reason that your Papillon is overweight, is: over feeding. Too many calories.
Buy him kibbles, offered as light dog food. Buy him a very good, nutritious , quality light food. you must read the labels very carefully. the first ingredient should be chicken or turkey, not fillers like corn.
I can recommend Purina One Healthy Weight Formula( first ingredient is turkey), available in groceries shops. Read the instructions on the bag, select the amount of your dogs supposed weight, take a measuring cup, fill in the exact amount of food for the day. feed twice/day, leave out for 29 minutes or so, and than take away the food.
And, as hard as it is: absolutely no snacks!!
Do not forget the exercise your Papi needs. Exercise will improve your dog's muscle tone, metabolism, and weight.
It might do you good yourself walking your dog. A dog is the best exercise program there is!!