As an obese person who tried several times to follow medical advise, this does not surprise me, not at all!
Every diet is about calories and sport, which cannot hurt. But every diet completely misses the elephant in the room: hunger!
Any medical procedure is only worth pursuing if it gives you a higher quality of life in the long term. A constant hunger cannot compensate for any weight loss.
And this is why a new drug just approved in the US for obesity is hailed as a game changed, NovoNordisk's semaglutide. (Wegovy) The "only" thing it does is mange the hunger levels in your body so you dont feel hungry all the time.
I think there was a study back in February for it which gave something like a 15% weight loss after a year, *on average*.
I did a sweet potato diet for a month a couple of years ago for medical reasons.
I was never hungry.
Switching cardio for resistance training (5x5) helped immensely with no changes in diet. My weight has dropped slightly, but my body composition changed a lot. Cardio became much easier after building some muscle mass.
There is also something addictive to increasing the weight you can lift, fits right in with gamer/nerd mentality.
Swimming also seems very effective, though I've not checked whether that effect's outside what's expected, or just normal.
As long as you're consciously making that trade off. Hunger vs shorter life, health conditions etc. I think that's a personal choice for the individual.