I've had plenty of experiences with the white devil and most people I know that have battled it for a long time are fatter than I'd think they "should" be. I think it's mostly because they drink a shitload to even themselves out. 1.5 oz of liquor has around 100 calories. 32 oz in a fifth (which most people I know that do a lot of blow can easily put down in a night) is around 2100 calories alone, then you have the mixer. It's not like they're doing blow all day, so they have shitty food that they eat on top of the 3000 calories they drink.
Just my guess.