Not him, but I found my will to lose weight when a close family member was told their liver was failing and they had a few months to live, due to cirrhosis from their obesity. I knew I was on a similar trajectory and my bloodwork showed a hit to my liver function.
Good news is that my relative also found the will to get healthy and their liver improved more than the doctors thought could happen and so we both are doing much better. I’m even under 25 BMI now after losing 40 lbs. Also amazing to be able to move around like I used to as a teenager again.
As to how, not very helpful but just using that fear to drive willpower to just suck it up and eat less and exercise even when I really want to be doing something else. It means to some extent just living with usually being a little hungry and almost never filling full for me. Changed the food for less calorie dense stuff and avoiding refined sugars of course, but still have to reduce food intake.