Okay, first off, the thing about wanting ot burn it off isn't good. With a mind frame like that, you can easily turn obsessive over food and eating habits. You shouldn't feel the need to exercise directly after eating. Yeah, it's good to exercise, but you need time to let the food digest and give yur body the nutrients it needs. If you exercise after, your body can't absorb anything.
Also, don't quote me on this, but I heard crunches don't do anything for you. Pushups are #### ### ##### #### strength. You need to work all parts. Do legs, arms, stomach, butt, thighs, or really whatever you want to work on. Instead of walking, do light jogging for a few minutes, then power walking, then walking.
Okay I'm not allowed to say 'good' 'upper' or 'body'? What? Ummm... okay. That wasn't inappropriate at all. Thats what the dashes are if youre wondering. I'm not swearing.