I don't know UK weights, but I can see he's overweight. I'm for leaving him with his family if they're willing to do what's necessary, even if he resists. I saw a mother on Dr. Phil with a young son who was obese, and she came back and thought it was great that, in all that time, he'd lost a half a pound! She claimed his weight was due to medical problems that the doctors just hadn't discovered yet (because the doctors said there was no medical problem). Since those shows, the father got custody, and the boy immediately began losing weight and is a normal weight now. He can run and he runs up and down steps every day for exercise. His favorite food is broccoli.

So, as I said, if the family is willing to do what's necessary, great. If not, get the child into a healthy environment.