You do not have to necessarily gain the weight again. I used to weigh 96 KG around 2 years back. The weight loss was definitely tough, but I got down to 83 KG in about 6 months time. I was on a Semi Aitkin as I would call it, loads of proteins, moderate fat and low carb. I did gain 3 kg back but am maintaining it at that.
slim person can get fatter and that is the reason why fat person can become fat again. Just that if a fat person could get fat the first time, it is likely that he gets back to his old habits and get fat gain after slimming down
Over the last couple of dacades, the famous diet programs in US would show headlines or ads that would show how Opera lost x pounds in a month and so on and so forth. If you think about it, at that rate of weight loss, Opera would have ceased to exist in a couple of years. No one writes about the weight she regains before following the next weight loss program to loss some weight. No one takes a step back and think how she keeps loosing 30 pounds of weight every month for 20 years...
Its all about making up your mind. Then consciously working on it for the rest of your life. The trick is to convince yourself that its good for U so you'll want to do it rather than consider it a chore thrust on U. The method can be any that works for U: Exercise and diet be it atkins,weight watchers,the zone,GM etc It's working for me so can't see why not for U