This page has an extreme example of metabolically fat as Id call it.Horses Health
That Appy is a little chuffy ( I think her neck conformation accentuates it more than what it is looking at what we can see of her rear) but I have seen much much worse. If that is an 8 or 9, These must have been 20s ;)
Here is a good chart if you can DL it.
Google Image Result for http://img.docstoccdn.com/thumb/orig/43288790.png
I once had a little stout grey QH built much like the OPs. She was also heavy on the front end. She could show ribs and look too light to me in the rear and still look heavy on the front end. It really depends on the horse. Id like to feet that horses sides and squeeze the neck and run my hand over the rump before making a solid judgement. Pictures can be very deceiving.