Questions about p90x?

My father did p90x and lost weight and gained muscle like crazy. I tried it but I guess it wasn't for me. I lost weight but the diet was to hard for me. My father lost 10lb in the first wk I lost 4 so it also depends on how dedicated you are my father did everything I only did it halfheartedly. But be warned the p90x will make you in shape if you stick with it. My dad has lost some 35lb since that first day.