Hi I tried the rested buff for the first time and then I noticed I received almost no damage from enemies, at that time I thought it was a bug with damage but now I remember the HP in stats was about 1100. after quitting the game and restarting it with the rested buff gone HP went back to 78 points.
Thank you for the report, we have escalated this internally
Found a way to consistently recreate that bug:
After you get rested buff you need to eat food that increase hp. After that, you will receive a massive hp increase for the duration of the rested buff.
In my case, i got up to around 5400 hp from 137 hp (25 points in health + 15% hp from gem) by eatin Sirloin Platter.
thank you for the repro we have identified the problem 