I once lost 15 pounds in 5 weeks, eating turkey breast and egg whites etc. It was someone's internet diet plan. The nutrition wasn't that bad, but I'm sure it was very low calorie. But I couldn't sustain it--and I had more than 15 pounds to lose. Plus I have never liked egg whites, and thanks to that diet, I don't like turkey anymore!
I broke down and stopped following that plan, and I gained back not only the 15 pounds, but another 8 to keep them company.
So that was yet another learning experience about weight loss. If you look at my top ticker, you'll see 43 pounds down from my highest weight. 33 of those pounds took me 8 months to lose--average a little over 4 pounds per month. But my weight loss plan was sustainable, and it could also be adapted to maintaining my weight.
So, please find a program that will help you lose weight safely and will also give you ways to keep it off once you lose it!
Jay