I think you could start with either. Power 90 is less intense and is better for beginners, but if you want to jump right into P90X, take the fitness test first to see if you can keep up:

http://www.extremebodyworkout.com/pdf/p90x-fit-test.pdf

-Mike

it could happen!! This might sound strange coming from a guy, but I know women have certain spots where they SEEM to lose more fat when they are working out. Some women’s breasts get smaller and for some it’s their butt! When you lose weight, it’s your body shedding body fat. You body sheds fat pretty evenly through out your body, BUT it’s the storing of the fat that can be uneven. This is one of the reasons why we are shaped differently. When you gain weight, where do you get thick? Besides the belly because that area seems to be pretty common for most people to gain inches! It’s those other areas that will slim down first. You may lose fat in your butt which will slim it down, but to tone and build muscle in that area, resistance exercises is key. Just like in your arms. If you want bigger biceps, you have to do curls!

-Mike

Power 90 will help you to tone up, yes. Be sure to keep your weights on the lighter side, not too light, because using heavier weights will build mass.

-Mike

this is always a tough question to answer because everyone is different in how they currently eat. If you want to eat healthier, there is nothing wrong with that. You can still follow the nutrition plan, but you might need to modify it so that you aren’t losing weight.

-Mike

if you aren’t ready to dive right into the P90X, Power 90 is a great stepping stone.

-Mike