Wild dogs have a mixed diet, not just meat, they also eat fruit and veg but the wild varietys not what we eat.

When I was growing up my uncle had a farm, he had a dog that wouldn't eat any food given to her, she went and caught a rabbit every day but she would also go into the orchard and get fruit, the vegatable patch and eat veg, and also go round when collecting the eggs for eggs.

Feeding just meat to a dog does not give them a balanced diet.

If your dog is overweight, you can also bulk out food with some veg, carrots go right through a dog but will help the dog think he is full, cabbage is another veg you can feed to aid him loosing weight.