FAA PPL Medical Class 3 check + weight?

There is no weight limit, however you will be limited in the aircraft you will fit in. Also, the health problems later on will eventually catch up to you.

If there is no underlying conditions due to your (over)weight, you should have no problem obtaining a third class medical certificate.

The biggest problem you are going to have is finding an aircraft that is capable of carrying someone of your size. I assure you, the typical training aircraft is not going to be of sufficient size. By no means, dont let this discourage you, it can be done, however, it is going to cost you a few more bucks for the difference in price in the trainer vs. a larger,more powerful airplane. I am thinking a Cessna 182 will do the trick as it has a useful load of around 1100 lbs and a higher rated (230 or 235 HP) engine

I've instructed students of your weight and they were not medically disqualified. Aviation Medical Examiners are concerned with whether or not a pilots stand a chance of being incapacitated while flying. If you have other conditions, they may pose a problem for you. Refer to the Federal Aviation Regulations, Part 67.

no problem if you want to be a private pilot.

problem can subsist if on interview for pilot jobs.