This is pretty much what I'm doing. I went to Weightwatchers last year and they promote a healthier lifestyle rather than simply a diet. I'm not sure if everyone knows about the points system they use? I'm allowed 18 points a day.....a slice of bread is about 2 points, banana 1.5 points, salad and most vegetables are free, fish is really low too. Alternatively, 1 scoop of chips from the fish & chip shop is about 10 points......some chocolate bars are 14 points! Obviously one scoop of chips or a chocolate bar wouldn't sustain you for long so the diet gets you to think about what your eating and making sensible choices. If you really felt like having chocolate, you could do but you'd need to eat mainly free foods for the rest of the day and it's just not worth it really.
I lost 15lbs and managed to keep it off (even though I stopped going to weightwatchers) until Christmas when I put on 7lb thanks to parties and chocolates and all the other evils that are attached to the festive season.
Now I'm eating a healthy diet again and going to the gym 4 times a week. My goal is 10 stone (140lbs) as that's my comfortable weight (I'm about a size 12......sometimes a 10 UK size). 7lb to lose and counting!
I'm exactly the same and also had to drink 2 pints of water an hour before an examination. I managed to last (thank god!) even though they forgot about me for 45 minutes!! I was ready to burst.
I've started to drink more water recently and have noticed, like Noll says, I'm retaining it more. So, my advice would be to train yourself to drink more. It's a pain at first and I do find myself looking for the nearest loo whenever I'm out and about but it's getting better