Shelley,

If you are looking into purchasing heart rate monitor ( if you don't have one already) then get one with calorie count. I have polar F6 and it's great, it shows how many calories you burned and Fat %. Also hills will train you harder , make your muscles stronger and your CV stronger as well. On saturday i did 40 flat miles burned 1295 calories with average of 17mph, i am 5'4" and 125lbs.