I'll openly admit that my weight gets out of control at times and I sympathies with you. The main thing I see with this situation is you are too heavy to board a PA28 as it has a 17st limit and unless your instructor is pint sized, performance on a C150 will be very limited, and not much better in a C152. These machines still form the backbone of the GA fleet but I'd imagine these fancy microlights they have these days will be more restrictive.
Look up VLCDs. It's a very quick and safe way to lose weight. You would be able to get on a PA28 in less than eight weeks and performance on a Cessna shouldn't be a problem. It's a pain losing weight, but this is the only thing that works for me. Anyway, that's way beyond the scope of this thread.
Good luck with your flight training. Hope you enjoy it. And I wish you luck on your weight loss journey too.