And why would someone be morbidly obese in the first place? Usually, it is because of lousy metabolism, which is caused by not exercising enough, too many crash diets, or nutritional deficiencies. Someone that is so fat that they would stumble someone if given a part is also so unhealthy that they might have a heart attack during the part, which would be far worse. They need reasonable exercise, a sensible diet (and no crash diets that will only make things worse), and supplements. Iodine supplements would help, and since most of us are deficient in magnesium (and a deficiency there can cause heart problems), I would start there.
What about the structure of the religion that can make one fat, or keep someone fat or make them even fatter? Most of their "exercise" consists of driving to a call or several calls, sitting in on studies, and sitting in boasting sessions. They might walk short distances in field circus, but never the brisk walking they need. If they go to any organized program to get in shape, the hounders will nag them about that. And the pious-sneer diet consists of too much "phude" at McDonalds every day. Hardly what I would recommend for anyone, let alone someone that is morbidly obese.
And what about sleep? What sleep? Do they really need all those boasting sessions or to get that 200 hours of field circus every month, plus work several part time jobs? A lack of sufficient sleep helps keep many of those jokehovians fat, or make them fatter than they otherwise would have been. Not to mention, every time something actually works, it is usually associated with martial arts or a pagan ritual--both are banned. How can anyone lose even a small amount of weight if most effective exercises are banned, as is yoga?