This area is a bit of a specialism for myself having worked with folk from various arenas in pursuit of leanness.. I can say that although slim folk may look healthy, there's an awful lot of unhealthy ones out there.. There are massive misconceptions about this whole area of fat and thin..
I have worked with people who have pulled out all the stops to getting lean, and struggled all the way to do so, having to endure harsh self denial etc, the slightest slip leading to weight gain..whilst others have simply given up eating Jamie Dodgers and became exceptionally lean..
This is about genetics and insulin resistance, the bigger baby, the more potential for fat cells, the more fat cells, the insulin resistance, the more insulin resistance, the ghrelin released to increase appetite, the more food eaten and so the vicious circle continues... There's a strong potential for addiction to food and unlike alcohol, you can't just stop eating food, thus the primer is always there.. Realisation and the urge to do something about excess weight, always comes at a time when all the support systems and lymph, water retaining ability etc are developed to carry such weight, thus you then have a set point..
there's not a lot we can do with what we inherit and only the switched on, committed and focused amongst us have any chance of decent weight management.. I do really feel for people who are classed obese, as in my opinion it is actually no different to being black or white and to mock someone for being either one or the other is indeed more or less the same..