I started "jogging" because I wanted to lose weight to look better. The more I got into my running the quicker I wanted to be and I knew the most effective way to do that would be to lose weight. Over the subsequent 20 years, I've taken action as soon as I gained a few pounds simply because of the effect it has on my running. For me, that's been a much better motivator than an abstract desire to look or feel better.
DP was lamenting to a friend about how he wasn't getting much female interest. His friend told him very bluntly indeed (using language I wouldn't use to anyone) that it wasn't surprising, he was fat and unattractive. That flicked a switch and since DP has eaten and exercised well and is now a very fit middle aged man with a DP 😄
I don't know if that approach would work for everyone, but DP basically decided he wasn't standing for it, rather than that he agreed with him. Most people faced with that would complaining about fat shaming?
I think most people who want to lose weight know what they need to do, but struggle to do it. If you've managed it, what was your turning point in terms of motivation?.