Importance of a slim waist- link.

[purplepeony]

news.bbc.co.uk/1/hi/health/8436409.stm

More info to spur you on.

I'm confused about this.I'm 5ft 7 and 9st 6,so definitely not overweight,in fact you can count my ribs and I'm a size 10.But I don't appear to have a waist and if I measure where it should be,it is 77cm.I wouldn't dream of dieting as I have struggled to put this much weight on [was 8st 7 until about 6 weeks ago when I started anti depressants,which cause weight gain.]If my waist or lack of it expands much more,am I at risk? How can I reduce my waist size without losing weight? I've never been on a diet or anything like that before,so am stumped for what to do.
THANKS.
FG