In August of 2007, I went on a 7-day buddhist retreat. The food there was phenomenal (and vegan!)
Right before the retreat, I did a 7-day detox based on the Martha's Vineyard Detox program. (The book is called 21 Pounds in 21 Days).. you can do the Martha's Vineyard detox for 2 days, 7, 14, or 21 days. I did it for 7 because I wanted to do SOMETHING before my retreat but didn't have more time.
It's very strict, and I found it extremely hard. I stuck to it religiously though, and I felt fabulous. Better than I've ever felt in my entire life! The 'diet' is actually NOT a diet. It's a detox plan, meant to get you healthy. I was having a lot of health problems and after a lot of research, I decided that this would be beneficial (and it was)... the great "side effect", if you will, is that I did lose 7 lbs in those 7 days. But again, my initial attraction to this was as a detox, not as a weight-loss goal, so losing 7 lbs was just an added bonus.
I kept the weight off until December by eating healthy (tons of vegetables, fruits, fish, brown rice, tofu, etc.) and then proceeded to binge on Christmas cookies and gain it back, but other than that, the results were great, I was healthier AND I lost weight. I would recommend you have a look at it, if you're interested. It's tough, but you will feel amazing.
"It is not the mountain we conquer, but ourselves." -Edmund Hillary