I lost 3 and a half stone in 2001, then a further half stone two years later and have kept it off. I did put a couple of stone back on in 2007, but that was due to medication, and as soon as I stopped taking that I lost not just that two stone, but another stone and a half in three months without doing anything.
That's all a bit confused, but essentially, I have lost around 5 stone since 2001 and have not put it back on again, so you can keep it off. I eat fairly normally, but in moderation; so if I go overboard on a weekend, I'll have a few really, really good days to make up for it. I am relatively active, but do no specific exercise like the gym.
I have been very determined not to regain the weight (it was horrific when I had to take that medication and watch the weight creep up even though I was eating the same way, and less), and monitor it by weighing myself several times a week. This means that I deal with any small weight gains of a pound or two immediately, while it is still easy, as opposed to having to deal with a stone or two, which, as we all know, is really difficult.