How can I get a 2 year old golden retriever to eat?

I recently rescued my golden. He was very skinny, and does not eat very much. The vet said he is at least 10-15 pounds under weight. He has had a complete health exam, and was given a clean bill of health. He has great energy, and plays a lot with my schnauzer. I have tried adding chicken, wieners, cheese, and other types of people food to entice him. He will eat a small amount, and then stop. He acts very timid around his food bowl. Even when I feed him with my other 2 dogs, he still is not motivated. Any suggestions.