This is a subject close to my heart.
My son is definitely on the chunky side - he weighs nearly 8 stone and he's the average height for a 9 year old. Like your son, copper, he's tubby round the waist. But then all our family on both sides weigh 'heavy'. Dh and I are both pretty average in build and my 4 year old is a wiry racing snake - yet when he is weighted at the clinic, his height is on the 75th percentile and his weight is over the 95th, so technically he is overweight. Yet one look at him and you'd see he isn't.
My husband gets very het up about our oldest son's weight. He really feels strict action must be taken by us all and is always commenting about his size to my son (not always critically, I add - my husband will also say if he thinks ds looks slimmer). However I think he is obsessing too much over this. Whereas my husband was average size as a child, I had a fat phase. I suddenly mushroomed at age 7, especially round the tummy, and didn't start to lose it till hit 11 years old. I never became skinny, but I did become average again. All this happened without any change in my diet or lifestyle. I didn't eat a Mcdonalds diet in those far off days of no fast food chains, but I munched my way through countless home made cakes and puddings, and always had a plate of buttery tea cakes after I came back from school, before my supper later in the evening.
My son mushroomed at exactly the same age as me, so I am hoping he will follow my patten. However I am not 100% confident. From the day they ewer born, my sons had different physiqus. My oldest son had a pronounced tummy always (even when he had no fat on it) whereas my youngest son did not, and developed far more muscle than fat. Both sons like their food. My youngest (4) has an average appetite but also drinks at least 1.5 pints of full cream milk a day.
My oldest, however, is very drawn to food. It's not that he loves junk food - he loves all food, and especially good food and he adores being taken out to grown up resaurants. He talks about these visits for months afterwards. He loves helping in the kitchen and can now nearly cook most dishes we prepare - macaroni cheese, stews, roasts etc. He can grill meat, make gravy, make cheesy mashed potatoes and other simple dishes unsupervised. He says he wants to be a chef when he grows up. He has packed lunches (fruit, sandwich, non fizzy drink and chrisps) not only because we can keep an eye on what he's eating, but also because he will take second and third helpings of any school meal going - vegetables, the lot! So in our case, his liking for junk food is not the main reason for his shape. It's his liking for food in general. But by getting heavy with him about food, I feel I am criticising and denying an intrinsic part of his personality.That's where my husband and I differ.
He is not sporty, but he is quite active on his bike and skateboard. However I do feel exercise (and some gentle limit to his eating) is the key for him to slim down. He seems to be stuck at a certain size at least - he is not getting bigger - so I am hoping he will grow taller in the next few years and even out naturally.
Going back to the report - I wonder what happened to the belief that many children get puppy fat and they will grow out of it?