I would have to say that part of the Happy Cubans happiness is that they live in a tropical paradise (if a dictatorial tropical paradise). If the sun was always shining and the cool caribean breezes were always blowing at my place I'd probably be doing alot more walking, swimming, biking, etc. The only exercise some Northerners get all winter is the heart attack snow shoveling. It's may also have something to do with the economic situation there (using what money you have to buy what you really need and walking to the store rather than driving the two or three blocks and having to pay for gas and insurance.
Discrimination based on size is as bad as discrimination based on any other factor. There have been many prejudicial mannerisms linked to certain races which have kept them out of housing, jobs, etc. Just because they can't do anything about their "color" and obese people supposedly can (although research has shown that at least a small percentage of people can't) is no reason why such discrimination should be allowed.
Is obesity a dangerous condition? As far as I know it CAN exascerbate other conditions, but this is assuming that the other conditions exist. It is possible to be obese and have fantastic cholesterol levels. It is possible to be obese and yet live perfectly healthy lives (as some studies of Italian people and their eating habits seem to indicate). This is still no reason to discriminate against obese persons. Smoking is a much more dangerous thing (which can be changed) and yet if a person is tidy and doesn't smell like a chimney they are much more likely to get a job when compared to an obese person.
I find it ironic that one of the most beloved characters in global society, Santa Claus, would not be given a job as a seller of toys because he is (Hey, I still believe damnit!) what physicians would say is morbidly obese.