Yep, this is a huge problem. The vet I worked for was a great dr., but terrible bed side manner

- he used to flat out say during an exam, Well, your dog looks great expect he's really
fat.

I would cring so bad and just look at the ground lol especially if the owner was overweight also, so embarasing, but he didn't care because it got the point across. As I would be checking some of them out at reception, they'd ask me all quiet, is my dog really that fat? Oh boy lol. He always referenced a chart like the one posted above and told the owners their dog's BCS (body condition score) and yes, many were surprized to see the way their dog should look, they thought it was too skinny.
The worst I ever saw was a client we had with a 60 lb. Corgi. It was their second one and they were very UTD on their vet care (check up every 6 months etc.) He was constantly harping on them that they were killing their dog (first one they was was HUGE, I mean could barely walk

and died of heart failure at 6 yrs. old

) but they still didn't learn and by a year old their second one was very obese. I just thought, how could they not have learned from their last dog?? Same vet and he told them over and over.
My beagle is 12 and has started gaining weight and I was freaking out lol but we recently diagnosed her with bloodwork as hypothyroid so hopefully after a few months on the rx she'll loose a bit.
LOL now I'm on a soapbox here LOL It's a pet peeve of mine though - Obesity is a human problem, not a canine one (or feline for that matter - don't even get me started there lol)