my parents were the same shape and weight when they married, same diet, same exercise, same everything. One got fat, one didn't. And what's more us kids took after them in looks, colouring - and shape too. (Fair, thin parent> fair, thin kids; dark, fat parent>dark, fat kids.) It's never a surprise to me when scientists say ooh, maybe there's a genetic element.
Fat people can lose weight through diet or exercise but it'll be harder than it is for thin people. Treatment can't be... to coin a phrase... "one size fits all". My own feeling is I just have to live with it.