The short answer is that fat people need to shed pounds as quickly as possible, so they need to waste as much energy as possible, and wasting energy is a “metabolic advantage.”
The correct answer is that, yes, a lowered metabolism is better for longevity purposes, and caloric restriction is actually a very good thing to do.
The concept is anathema in the ketogenic world, but Dr. Bert Herring goes into how one can be low carb, calorically restricted, metabolically efficient, and lose weight through an appetite correcting eating schedule.
I had a period of very rapid weight loss from the time I started a ketogenic diet + Fast-5, up until the time I listened to a thought leader’s warning that if I didn’t “feast” that I would ruin my metabolism with one meal a day. From that point onward, I’ve been plateaued. It might have happened anyway, but I followed the advice of “feasting,” trying to fast, feeling awful, and then eating because if you feel awful when fasting, that’s what you’re supposed to do.
I avoid this forum for a long time because that thought leader is held in such high esteem, although trying to follow her advice really messed me up.
The problem with time-restricted eating is that once you go away from it, it’s so hard to go back to it with the same zeal. I’ve managed to push my weight down to 209.5, but it’s back of 225 and I’ve been stalled at that point for a while.
Anyway, the hypothesis is that if you follow an OMAD type approach (although my five-hour window allows more than a single meal, if I’m still hungry later, which I rarely am), your body will eventually realize it has extra fat to burn and your appetite will self-correct, plus you will enjoy the longevity benefits of not “boosting your metabolism” first thing in the morning.
I hope this helps.