<human>: Give me the gist of the text in a nutshell

My grandpa - a very intense and spry gentleman - loathes fat.  I guess he's been this way for a while, since my aunt has an eating disorder and my mother, who is naturally curvy and maybe 40lbs overweight hates herself, diets constantly, and has refused to be photographed for years.  He's merciless and cruel to my very stout dad and laments how beautiful his ex-wife was before she let herself go.

I'm the lucky aberration in my family - naturally skinny and slightly underweight - but I still try to eat very little as I'd like to loose 10 lbs to attain model status (Which I kinda recognize is stupid, but I'm also terrified of the random weight gain that seems inevitable with middle age).  Grandpa keeps emailing me pictures of thin girls and telling me how I'm beautiful just like they are and how I shouldn't share them with my mother because they'll make her feel bad.  Given that my mind's a little screwed up already, how can I tell this well-meaning, but insanely "I'm always right" gentleman to shove off and leave my body alone?
<bot>: Grandpa has foisted his obsession with weight on my mother, and now won't stop talking about how skinny I am.