I hate this too.
Story from a couple of years back, but typical.
I was at work at the time, friend and I were in the lounge of the Care Home we worked in, with the carers (I was the cleaner, friend in charge of laundry). This week we had in a chef who cooked cakes from scratch, and had at this point come in with home made doughnuts.
The conversation existed of friend and I accepting the doughnuts, saying they were delicious and carrying on chatting about nonsense, not anything important.
The carers, all three of them refused the doughnuts, talked about how fattening they were, had a biscuit each, went on about being 'good', and 'bad' with food, and by the end of the break, had had three biscuits each, which I found out later had been some doughnuts too.
Guess who was overweight?
I found it boggling.
The reluctance to eat the fattening food, and the obsession with it being bad, was only in those who were overweight.