Hello!
Nope, I don't think it's an unrealistic goal per se, but it may be quite ambitious, particularly if you aren't very overweight at the moment.
When I was much heavier, I found it fairly easy to lose consistently and regularly (1 - 3lbs per week), but now that I'm a healthy weight for my height (according to BMI, anyway!), I find that my weight loss has slowed down quite a lot. I suppose to maintain my rate of loss, I'd need to adjust my calories down and eat less, but that's not really something I'm prepared to do (I calorie count, and find if I try to go lower than 1,500 a day, it just feels really bleh and too restrictive, and thus difficult to stick to!). It sounds like you might have similar feelings on that, in that doing something really "diety" doesn't seem to appeal!
Doing exercise is great and will definitely help you loads, particularly if your goal is to be healthy on the inside, rather than just weigh less! So yep, definitely an achievable goal, and it sounds like you're going about it really sensibly. Best of luck!
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major goals: healthy bmi @ 159 (achieved 13.11.10) | original goal @ 150 | ultimate goal @ 138
stone goals: under 12 stone @ 167 (achieved 19.09.10) | under 11 stone @ 153 (achieved 17.02.11 ...and again 29.04.11!) | under 10 stone @ 139
c25k: completed! (started 30.08.10, finished 08.11.10)
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