Body fat loss and maintenance is an outgrowth of fitness, not the other way around.
People who have a heck of a time getting weight off and keeping it off, will ask me where they can focus effort. My answer: strength.
The lower your strength, the less force you can produce in everything you do. Look at this however you want: calories, macros, hormonal signaling. The end outcome is dependent on muscular strength. A person who can generate 1000lbs of force at the hips burns more calories, distributes macros better, and beneficially signals hormones above and beyond a person who can generate 100lbs of force at the hips... during a slow WALK.
So people get stuck in a trap. They realize they have to run to progress past their walk. They have to walk or run 10 more minutes, 60 more minutes, 5 hours more per week in order to continue losing fat. Meanwhile, a strength athlete who can now produce more force at the hips burns more calories in a 10 minute walk than they used to in a 20 minute run.
Lack of strength doesn’t scale. It can’t take you forward. It’s putting the cart before the horse.