Firstly and foremost and underactive thyroid does not make you fat.
I have an underactive thyroid and it did not cause me to put on 2 stone eating 6 donuts one after the other, sweets and shit did.
Having an underactive thyroid did not stop me from losing 2 stone. Im still what I call fat as Im a size 12 at 5ft 2" weigh 10 stone. Need to lose another stone to get rid of my pregnant stomach, but why haven't I? Cos Im too fucking lazy.
There really is no excuse for fat other than lazyness, being on the other end of it being fat and eating too much is what I did which caused me to be a size 16. I was huge and round.
Why? Cos I ate too much and sat on my arse all day long.
Sorry but I agree with the OP and having experience of it and having been through it I totally understand why she has posted what she has.
Go flame me if you like, but I have been fat, I'm still fat and I'm only fat because I eat too much of the wrong foods.