It's a bit easier to keep your weight down when your younger, i'd think that if you can get yourself out of bad habits early it will be less of a pain to keep that 11 stone or above and not add a couple of stone later..
I myself am 5 foot 5 and weigh between 12-13 stone it's really hard to lose the weight and my metabolism isnt that great anything i eat go's straight on my stomach and under the chin
A good habit i have got out of is buying 2 bottles of 2 litre coke a week and drinking it to myself over the next 3-4 days, i now just have dilutable and/or fruit juices.
That took away 1/2 a stone of my weight with-in two weeks
Now just to find a way to lose the other couple of stone to go with it, and not get it back on again.
At 19 i was 9 1/2 stone and im 30 in two weeks and i weight 12 stone 8 at the moment.