I did some research. He is down around 25 pounds to his normal walking around weight. There are several websites that have information about his weight loss during his illness. There are rumors he got as low as 240 but nothing substantiated. He was on a very meat rich diet with low fiber before his illness. Since his illness he has changed his diet, has a new dietician and he is not regaining the lost weight very fast.
Prior to cutting weight on the first Mir fight he had to cut from 295 down to 265. His last fight he only had to cut from 275
down to 265. According to the website bloodyelbow.com Lesnar had already made weight a week before the fight. He didn't have to cut any weight the last week.
I am sure he will get back to the 285 plus weight level but it is going to be a little harder than it use to be.
You can check out MMAJunkie, MMAmania, Sherdog and MMA fighting websites for the details.