Well,.... I'm female, 5'6" & about 200lbs. Yes..... that puts me in the category of being obese, by the medical profession. I say this not to brag in any way, that's just the way it is right now. I am working on slowly losing the weight; I didn't gain it fast & I won't lose it fast. However, despite being heavy, I am quite active & still quite flexible. Just a few weeks ago working as a dive master for some check- out dives, I had to rescue a student who got into an uncontrolled descent & froze up. I caught him at about 70ft. Because he was frozen up, I had to do all the work to get us back to the surface. At the end of it, yes, I was breathing quite hard (part adrenaline pumping & part, yes, I could stand to be in a bit better shape), but I got us both up safely. As a brand new instructor, I have yet to teach any students myself & that will be after some mentoring from more experienced instructors. I have had to demonstrate all the skills required in the course & then some, although a little practice to get them perfected is needed, it never hurts to keep working on the basics. My IT/IC did not take it at all easy on me, just because I'm heavy. He expected exactly the same out of me as he did the others in the class. Just because someone is overweight, doesn't mean that they should or shouldn't be allowed to do something. As was stated above, some with limited range of motion have to develop ways of working around the problem. As was also said above, don't judge a book by it's cover.