I lost 100 pounds over the course of 1 year a few years ago. I was a heavy over eater, surviving on super-sized fast food meals twice a day plus snacking. I began by eating a similar quantity, but switching entirely to low fat, low calorie foods. I spent an hour in the grocery store every time I went examining labels on everything to make sure I was getting the option with the least calories and fat. I literally went in, threw EVERYTHING in my fridge away (even what was still good) and replaced it all with these substitutes. That alone sparked the initial loss.
I then began lowering the quantity I ate, and eventually switched to Slimfast, but once I got my over-eating under control I could substitute a shake with something else that had similar calories and fat content from time to time for variety. I also switched completely off soda and drank nearly a gallon of ice cold water a day. I just always kept a glass with me where ever I was and still do. So that I wouldn't die of cravings, I let myself have one "bad" meal on Saturdays... I could eat whatever I wanted but it usually made me sick because it was usually greasy and my system wasn't used to it anymore.
The key was... walking. I was completely
sedentary up until then, and I started walking just a mile at least 3-4 times a week. If I didn't walk, I didn't meet my goal for the week no matter how well I watched what I ate... it's that simple. I bought a treadmill this past New Year and I quickly lost interest in it... I would much rather walk outside but I now live in an area where I don't feel comfortable doing that just yet (too many neighborhood noseys watching!).
I gained about 55 pounds back because I stopped walking... and have really allowed myself to eat poorly when I know better.
Fad diets don't really equate to the life change it takes to lose and keep it off. I haven't gained all the weight back and consider myself still 'watching what I eat'... although not as vigilantly. I will always have to watch what I eat, and I had better start walking again or I'm going to end up back where I started.
So, moderation and movement my dear, that's my advice.