I'm a bodybuilder, and let me tell you something, walking does NOTHING. You can very easily take brisk walks every day for the rest of your day and not lose a pound. Low intensity cardio (most stationary bike and aerobics programs, etc) has been proven to be near-useless when it comes to losing fat.
On the other hand, high intensity cardio (jogging, sprinting) does wonders. Try jogging for 20 minutes a day, and watch the pounds melt away. Or you can continue taking your brisk walks and pretend they're actually doing something just like every other person who's too lazy to put more effort into it.