A few weeks ago, my mother in law actually told me that to gain weight, i just needed to eat more. It was all I could stand so I put it out there and told her, sure... except when I eat, I throw up and have violent spasms where I drop about
a pint of equal parts of D and blood. Her face went white and she said "I am only trying to help." That was actually pretty tame compared to what I felt like telling her, "Yeah... I never thought of that. To gain weight, I have to eat more? That's brilliant. Just like for you to lose weight you just have to eat less."
I know it isn't meant to be ill-intentioned, but at some point people just have to back off.