I could make an argument that obesity is self induced.
That it is. It may be rooted in psychological causes both genetic, environmental and acquired, but it is (almost) never the result of someone else force-feeding you, so any and all motivation and incentive have to come from yours truly and nobody else.
Oh, and coming down from semi-obesity isn't all that hard (unless you're in a hurry). In the past year I've come down from 150+ kg to 96 kg today over the course of 13 months doing nothing more than eating at least one healthy meal each day (usually a 500g mixed salad), and only one serving at the other meals. I still eat junk food now and then. I still drink sugar-filled sodas. I still eat candy and chocolate. I don't exercise more, although I do tend to walk more. So it is possible without weird diets or exercise from Hell.
So I tend to say that failure to lose weight is caused only by the person itself. It doesn't take much change to do it so failing to do that is bordering on pathetic.
I spoke to a doctor specializing in diets once, and he 'revealed' that losing weight is beyond simple: Just use more energy than you eat, i.e. eat less or exercise more. Do that and don't cheat and you will lose weight. Eat more smaller meals and your metabolism will increase, thus using energy faster. Avoid mixing carbon-hydrates (sugar etc.) and fat and you can eat either without it ending up getting stored.