If you're question is if you work out for 30 minutes of walking (cardio) will you still lose weight. I'd answer by saying it's a start. You can start off with 1/2 hr- 1hr a day, for a couple of weeks & you'll see changes. It's more beneficial to add more activity such as jogging running aerobics and or even weight training as the weeks go by.
If it's new -- if it's the same thing you've always done then no. You have to make changes to notice changes.
Exercise and Diet will help you lose weight!