If you don't need to lose weight, but you'd just like to shape up a bit, why not do what I do and walk to places whenever you can. I was getting pretty sedentary a few months ago and decided I wanted to be more like my old shape but didn't want a load of faffy diets (especially since I'm an ex bulimic and have to be very careful that I don't start to "play" with my food). Since then I've been walking to and from work (about an hour in total) and I've shed almost all my annoying flabby bits. I also feel healthier.
The others were right to be concerned when you said you wanted to lose weight but didn't need to. There may be no cause for concern, but perhaps you could just double-check your motivation for this to be on the safe side. These days I'd recommend that people think less about weight than inches: inches you can work on as long as you accept that some aspects of your shape are simply there, like 'em or not, but weight is always such a difficult thing to measure in terms of what's right for each individual. Sorry if I'm being a bit preachy, but diets are often motivated by complicated things, and also have such a tendency to go bad and cause more problems -- and I learned that the hard way!
All best wishes,