They have special BP cuffs designed for fat fucks, and you have to spike the pressure through the roof to get it to work properly.  Even then, it's really hard to hear what you're after even with an incredibly high quality stethoscope.  I've had to do this a lot of times and it's a lot harder than with a normal weight person.  I have yet to find a lardass who isn't hypertensive.  Every time I hear some land whale claiming that they have good blood pressure, I know they're lying.  Blood pressure skyrockets when the heart has to pump gravy.