I had the same problem myself, and you probably don't want to hear this, but fat going on round the belly is not a good sign, from the point a health pov - it suggests you may have a disordered insulin metabolism (often called syndrome x or pre-diabetes). This can be reversed!
Any increase in activity levels would be good, even just a daily brisk walk - activity helps regulate blood sugar.
The big issue is diet though - I would suggest reading up on low carb diets and syndrome x, and see what you think about that - if you give in a go for a month or 2, you may be amazed at the results! I know I was - and that was 7 years ago, I have kept it off, except for a minor blip for a few months following the birth of DS4!
I am approx 3 stone overweight, most of which I gained after having 2 children in 18 months. Before children I was a size 12-14, so not thin, but had a relatively good figure, sort of hourglass shape. Now I've gained weight which I am getting ready to think about losing as it's starting to get me down. The thing is, I seem to have gained a lot of the excess weight on my tummy, and my shape has completely changed. My tummy is massive now, and my legs and arms etc have stayed relatively slimmish. As I said, i would like to start shifting this weight. Can anyone recommend a diet/exercise plan that will help me lose weight from around my middle as this has definitely become my problem area? I have nightmares about losing weight from my boobs/legs etc but still being left with a horrible sticky out tummy!