I've been trying to lose weight -- with some success, actually, as I have lost 8.8 kgs (19.4 lbs) -- by using the Weight Watchers system and combining it with what I know about nutrition and diet.
It helps a lot if you can exercise while you're trying to diet. My knees won't allow me to run, which is my favourite exercise, nor really to cycle (going up hill is too painful), and though I try to walk for an hour a day, that only "uses up" 4 points (I am "allowed" 39 points of food & drink per day). Swimming on the other hand "uses up" 16 points in an hour. Of course, it's much more vigorous than walking (I can't walk fast because of my knees), but all the same, that is a huge difference.
And ... having lost all those pounds of fat, I can wear nice swimwear, as my tummy is now quite small. Today, I wore my Speedo Solars. And no, these pictures are not of me! But give me another 18 weeks and I will have no paunch left. I only discovered how effective swimming was two days ago, and I am already up to 24 lengths at our local pool. But my shoulders and arms are really tired now.