On the plus side, you can build massive arms and shoulders from simple push-ups when you are overweight. Don't need no gym, at least, if you like that sort of be-scared-of-me look. There is no way an obese, say, over 120 kg person could master the 100 push-ups challenge and not have brutal arms and shoulders. However, it will not be 7 weeks, more like a year.

This is really the primary silver lining obese people tend to forget. Just throwing that kind of body around, like playing tennis or going boxing, builds massive muscles. I tell obese people hardgainers probably already envy your calves. One of the hardest muscles to grow and poof you got it for free.