Lweji, no, I think you have it the wrong way around, the greater your body mass, the more energy it takes to move around, therefore you need more calories to maintain that weight and reducing it would lead to a deficit. So in theory, someone with a maintenance level of 3,000 calories would lose weight by reducing intake to 2,500, something that someone with a maintenance level of 1,800 obviously couldn't do. As weight drops then calorie requirement would drop. Same reason why men tend to need more calories than women - they are typically bigger and have greater muscle mass (which is more metabolically active).
As for the 'debunked' predisposition, there's more and more evidence to show that gut microbiomes play a huge role in whether we tend towards obesity or not. Google the experiment with mice and fecal matter transplants from overweight subjects.
Also there's a theory that we all have a 'set point' of body fat that our body will fight to maintain. This set point can move up if we stay overweight for a sustained period and it is difficult, if not impossible, to shift it back down.
Added to this, each diet when weight is lost (for most people, the exception being those who weight train and eat very carefully) means less muscle because when deprived of food our body will prioritise hanging on to fat. Once smaller of course, our calorie requirement is reduced - see above. If weight is then regained then most of it will comprise fat (because muscle is hard to build and requires lots of protein and training). You may get back to the same weight as you were pre-diet but because your body composition has changed to have less muscle and more fat, your calorie requirement is lower than it was (because muscle burns more calories than fat does), so the next diet is harder and each cycle like this compounds the effect.