Is this morning walking good for me?

Now I have committed myself at the joy of my puppy roxy to go for a 45minute walk every morning. Now i am told that to start burning calories I need to walk for at least and hour. Anyway I think it is good that i am getting out anyway even if i only burn 50 or so and i could even extend it a bit but i think it is a good habit to have Could I have someones opinion on this? Thanks in advance