Hard disagree.
As for practicality, weight loss is a function of thermodynamics. Caloric deficit == weight reduction. Doesn't matter your physiology.
As for maintainability, well that certainly depends on how a person is taught to diet. If you tell someone they need to eat less to lose weight (which is what almost every diet does) then, yes, it will be hard to maintain. If you tell someone to eat more (low calorie) food then weight loss is easy.
Most obese, untrained people will very readily drop tons of fat weight with little stimulus.
When I diet (whether the intention is gaining or losing weight) I'm probably eating 2x as much food as an obese person who is wondering to themselves "why is my metabolism so slow?". It's not. The foods I eat just contain less energy than the foods they're eating.