Sue L,

Congratulations on your success to date! Including exercise on a regular basis will help you reach your goal. In fact, for most of us that want to lose body fat, exercise is a must! And although walking is definitely good for you I think you would burn more fat if you did strength/resistance exercises. I'm going to provide some references below. Perhaps this type of strength training would work for you. It has worked well for me!

"The Slowburn Fitness Revolution" a book by Fredrich Hahn (info at www.seriousstrength.com)
"The Power of 10" a book by Adam Zickerman (info at www.informfitness.com)

All the best in your quest!

Andy