Yes! The calories you need to maintain your current weight differ, depending on what your weight is, it is linked to your Basal Metabolic Rate. For example, a 30 year old woman at height 5' 6" will need 1920 calories to STS at 13 stone (assuming little exercise), but only 1800 calories to STS at 11 stone. Ok it's only 120 calories per day but you can see how easy it is to sneak a few pounds on if you're not careful.
Exercise is the key (dammit, lol), if that same woman did an hour in the gym three times a week then she'd need 2325 to STS at 11 stone, quite a difference.
Thanks for the website. I know I need around 1960 to maintain at the moment, but I'm just dreading the thought of eating 100 cals less to lose weight.... I execuse slot already damn it !! Hehe. I think I'll drop 50 cals every stone bracket :0) x