Hello and welcome to the forum,
There are so many variables and each dog is different. Most have us have just settled on a food that suits through trial and error. My dog was a little underweight when we got her but I just fed her the recommended daily amounts and she stabilised at a healthy weight in time.
There is so much choice and if you want any information about a particular food, hopefully some members may have had some experiences to share. Also there are lots of threads about various foods to browse through. It is fairly easy to order online which gives you more options than what is available at PAH.
You can also look at this thread
to see how to search for a suitable food in the dog food directory. It should give you some ideas. I hope this helps. Good Luck.