A friend of mine dropped a lot of weight like that and ended up having to have her gallbladder removed in emergency surgery. Quick weight loss can sometimes cause gallstones.
In the long run, losing excess weight can help people with obesity lower their risk of developing gallstones. However, while in the process of rapid weight loss, gallstones can develop for the same reasons as obesity — it alters the balance of cholesterol, lecithin, and bile acids, and affects gallbladder function.
““Additionally, during rapid weight loss, hypotonia of the gallbladder can make it function poorly, so bile stays in it, gets stagnant, crystallizes, and forms stones,” Dr. Ahmed says. “As more cholesterol is getting excreted, the bile becomes super-saturated and the gallbladder emptying being less effective, leading to stones.””
I’ve done it without gallstones or other ill effect. All benefit. I actually think that an otherwise healthy person doing what I outlined (with the addition of lots of salad vegetables w/o sugary or processed dressing - I forget to mention this) is unlikely to get gallstones. Hey this is free advice FWIW so take it or leave it. But a dude this heavy is at risk of many, many bad things so personally I would say he needs rapid weight loss pronto. If he listens to the go-slow approach of mainstream medicine, it will take him years and I would fear that he does not have that long.