[Baroness]

I personally wouldn't say anything, unless the person was asking and needing advice and mentioned it to me. Someone I knew, maybe...but unsolicited advice never turns out well in my opinion. Weight issues are a very touchy subject and some people will get very upset, and take comments the wrong way, no matter how well meaning the person making the comments is trying to be. Saying something like, "yeah my pup had that issue, or my parents dog had that issue, and we tried this..." would be something that you might be able to get away with without offending, but otherwise I would leave it be.