View them like addicts, with a diminished mental drive to excercise, major self esteem issues and other mental problems where food actually triggers positive feelings for them, then makes them feel guilty which in turn makes them want a source of comfort which, is food.
Then realize they can't just stop taking their drug, it's essential to live, things soon start to pile up and many issues plague them. At the size that they would probably need a scooter, they would have fuck all fitness and merely moving their body with walking would probably wear them out in a few steps.
Yes it's self induced, but without a lot of support and POSITIVE reinforcement it is extremely difficult for them to get past it. If you just give them shit it will probably upset them, make them wanna comfort eat more.
Yes they've probably given up, not everyone has the same amount of willpower, we all suffer from illness at one point in our time, whilst it is self induced there is some responsibility in genetics, society itself, hell people around them, cultural issues, and more which people will just say is an excuse.
Obesity is more than just 1 problem.