I have tried a lot of workout programs and diets and the one I have found to be most successful at losing 20 lbs fast is . . . are you ready . . . give birth to an almost ten pound baby! That's the only way that I know of that you can lose weight fast, otherwise it is a long drawn out process!
Getting healthy is key in my opinion to being an involved parent, before I became pregnant with N I weighed the least I had weighed in a long time (probably since my freshman year in high school) and I found that I had so much more energy and could do so much more with my kids.
My personal goal right now is to get back to my pre-pregnancy weight by August 15 that is 3 months after N turns 6 wks and I can start really working out, and that is how long weight watchers gives me to get back to my lifetime goal. From there my other goal is to get flat abs within a year from the day she was born so every Friday I am going to post about my progress and things I am doing to help me reach my goal!
I strongly encourage you to set a goal to get healthier and set a date for when you want to achieve that goal, then make a plan to make it happen!