[snootyjim]

I'm 6ft, 13 stone 6 or so at the moment, looking to drop down to between 11.5 and 12 stone in the future... admittedly I haven't succeeded (because I've only recently started being proactive about the situation), and I know very little about the biological side of things, but what I would say is this:

Only ever do what you find motivating.

In the past I thought I was much too busy to exercise (and being at school doing A levels I was probably half-right), so I figured that the key was my diet. However, putting myself onto some ridiculous diets I'd come up with, such as my "dinner is all you need" diet, just completely demoralised me and made me extremely depressed - I love food, and I make no particular secret of it - sitting there denying myself food all the time just made me think about it constantly and took me to the point where I was so demoralised I gave up.

Obviously you don't have that same kind of issue - evidently your diet is okay - but the point I'm making is that if you do anything that you aren't happy with you'll never make any progress. If you go out running when everything aches, and get home with everything aching even more, you'll just feel rubbish and probably be less inclined to go out the next time. The longer it goes on, the worse you feel and the less likely you are to come out of the other end.

Start with what you're happy with, even if that's just a 15 minute jog or a long (and fast) walk, and then see how it goes. If you're doing too much and it's leaving you dissatisfied, cut down, or if you feel like you've got more energy to burn then up it a little. You might be able to force yourself through a harsh regime for a fortnight or so, but unless it's something that you can continue on a long-term basis then it's completely worthless, so just do what you're happy with. After all, being satisfied and happy is far more important than your BMI number on a chart.

If you wanted to keep a diary, I'd thoroughly recommend it - my girlfriend is watching over my progress which is fine with me, but however you manage it, if you put a bit of information out there then you'll get people there to encourage you and give any tips/advice on a daily basis about what you should try or do differently on specific occasions when the norm might not be appropriate. Even just to post your progress on here would probably be useful, it helps you gauge how far you've come and I'm sure you'd get a fairly decent crowd who'd check in every now and again to make sure it's all going smoothly.