I'm late coming to this thread, I know but I recently dropped from 99kg to 78kg in 7 months.
Now I hate exercise and I smoke, it's not a healthy attitude or lifestyle I know but it's how I am, so I did this completely by diet alone. It was a good ol' American 'low/no carb diet'. I didn't go super strict but to break it down to the simplest terms; anything containing flour, sugar, potatoes and/or rice is the enemy. Cut them out completely and you'll start to lose weight.
It ain't easy, it chops your eating options by over 50% and you haven't had a carb craving until you have bolted across 6 lanes of moving traffic to get to an open Brumbies Bakery on the other side of the main road like I have. It's about willpower and replacing your carbs with protein, meat is your friend here. One of my favorite packed lunches for work is a simple lettuce, tomato, cucumber, olive and feta salad with kangaroo sausage chopped into it.
However I am NOT a dietitian but even I am aware that this is not a long term sustainable diet. But if you can keep it up for 6 months then you'll probably have your eating in check by the end of it. God knows I have.
I should probably mention that for all my preaching about cutting out carbs, I never once considered cutting beer from my diet. It was my one exception to the rule. However I did resolve not to drink any booze except on the weekends. All in all, if I was going to have a diet blow-out (and they happen) I saved them for the weekends. One or two days out of seven isn't the end of the world.
One final point, since I've dropped the weight I am more open to the idea of exercise and have taken up a once a week boxing class. It isn't much but it's a start and that's all we can ask for. It doesn't seem so bad now that I'm not lugging an extra 20kg about.