Well I'm not a nutrionist but I did lose 41 pounds two years ago and have kept it off but I swear it's easier to lose it then keep it off that's for sure.
Yes, Yes, Yes it's the old adage - calories in and calories out..even the Biggest Looser peeps preach this constantly. You can still do low fat, low carb, etc., etc. but it's the calories you put into your body vs. the calories you burn through everyday life and exercise.
Oh my..I hate to break it to you but the older you get the harder it gets to keep the weight off..your metabolism slows down tons.
Good luck and hope you are able to fit into that dress soon.
Hey I love the new show Cook Yourself Thin that's on Lifetime they say you can drop a dress size in 6 weeks if you follow the recipes. You can check them out on line or get their book.