It's all about will power.
As a sober alcoholic in recovery, I disagree. Will power is naff, it only ever got me so far, then the wheels come off; it's limited in it's value (though not useless).
My suggestion would be to get some strategies in place. For example, I don't like running, but I run. I'll do this by arranging runs with other people (and a dog); if I've got a set time and place to meet someone to run, I'll be there; it kind of removes the power of choice from me. Left to my own devices, I'll probably not bother, because I'm lazy like that.
I also find that spending time with a bunch of folk who all suffer with the same problem as myself a great help. For this I go to an anonymous organisation, which is actually full of smart and funny people. One of these guys is also a member of Over-eaters anonymous, and he tells me they've helped him loads.
http://www.oagb.org.uk/At his heaviest he was 23 stone; now he's around 14 stone and has a very good diet; but more importantly, he has strategies that help him maintain a decent weight - and stay sober - and be happy about not abusing food or alcohol.
I personally think food is a tough one; it's 'easy' for alcoholics; they just have to stay away from the first drink - that's not so easy to do with food; obviously.
My suggestion wouldn't be to rely on will-power. Even this shock you've just had, Gerard, will only last for so long. In a few months, once the shock has worn off, you may find - without any good strategies in place - that you're back to doing the same old things and getting the same old results.
Find a bunch of people who suffer with the same thing as yourself, and learn from the guys who've solved their problem. If it's anything like booze for alkies, it'll not be an eating problem, it'll be a thinking/feeling problem.
Whatever you choose to do, I hope it works out for you.
Regards
Tosh