Rude!
Womanly bodies come in all shapes and sizes. Someone who goes to the gym still has a woman's body. A slim woman still has a womanly body.
You could argue that someone who puts effort into keeping healthy has a far more "sensible" body shape than someone who is overweight/obese (speaking as someone who is)
No women I know and see at the gym have an "adolescent boy" physique - that's not what the gym is designed for - there's a huge mix from strength trainers who are visibly muscled, women carrying excess weight, and even the "slim" women are aiming for, and do exercises specifically to achieve a curvy kardashian type body, with a large butt and defined curves, than very skinny.
All the "very slim" women I know don't go to the gym at all and keep their weight low by restricting food (and smoking). And even they have a "womanly body" because, again, women come in all shapes and sizes.
Apart from anything else, everyone suggesting OP might be "big boned" seems to have missed the part where she was very slim when they first met. Her overall body type hasn't changed, because that's physically impossible, she's just put weight on, as most of us do as we get older.
It sounds like his comment was insensitive but accurate. She is bigger than her friends. A size 14 is bigger than an 8, 10, or 12
(Again, I am a 14 BTW and fully aware that I'm bigger than slimmer friends, though I would still probably be upset if DH mentioned it).
He could apologise for being a bit insensitive but everything else seems like a huge overreaction to what is essentially just a factual statement.