I have a tip about losing weight, you might be able to lose the first 10 pounds quickly and relatively safely. After that, you are in danger of developing gallstones if you lose more than 5 pounds a week. Plus you won't be helping your fitness.
The PA 400k isn't too horrible, although the first half has constant climbing. I had trouble last time because the first control restaurant was closed and I needed some real food at that point. This was pre-covid, so I have no idea if they'll be open.