Well these scientists may well know more than you do.
Until we find out for sure, I’m know what I see. You know that you are absolutely right.
We’ll find out who is in time.
I’m not saying there can’t be other causes, this whole discussion would work a lot better if you didn’t make assumptions about what I’m saying, stick to what I write because 100% across the board every one of your assumptions has proven the old rhyme true.
Certainly we know of body type and glandular issues. But that doesn’t change certain facts. And among those facts are that you and your niece did crash dieting and you present that as evidence against something that isn’t crash dieting. And the diet you’re saying you used but actually didn’t actually does work, and works very well, is the basis of the most successful weight loss programs in the world, and is the method used by doctors to deal with morbid obesity.
Eat less exercise more DOES work for the majority of people IF they do it right. Doing it right means DO NOT turn it into a crash diet, DO NOT go into starvation mode, and DO NOT go back to how you ate before when you achieve your goal. Doing it right means stick to it, don’t expect instant results, don’t let the plateaus get you down, and understand this is a 100% change in your lifestyle. And doing it right also means find you if you’re part of the minority with some sort of pre-existing condition, don’t fight your own genetics.