I'm no expert, but here's the sequence (in reverse order) as I see it (for now): bad-things-happening Anything that treats "bad things happening", or "crazed immune system", or "crazed gut bacteria", will be a bandaid. I think our first world lifestyles create a perfect storm of bad living that undermines the foundations of a healthy human being from a multitude of vectors. Not enough sunlight, not enough unprocessed…
And you know what ? We know that many Pharaohs of ancient Egypt had it too, including Ramses II : https://www.ncbi.nlm.nih.gov/pubmed/12548434
So long for the 1st-world, industrialized society as the root of all evils...
Moreover, sounds like your friend was on biologics. Sure, losing 75pds will help lowering the inflammation and pressure on articulations anyway. But there's NO evidence it's not just a pause in flares, sorry for your friend. I met many people with AI diseases and to date have met no one who can prove he "healed" with a change in diet. Happy to discuss about it in PM if some read that comment !