In relation to losing weight the absolute best time to do Cardio is first thing in the morning with no breakfast. This is called a fasting cardio workout as you have not eaten since the previous day, sometimes up to 12 hours fasting. This leaves your body somewhat depleted of the usual energy stores and it has only fat to attack. You can read more about this in the stickies in the general exercise forum.

I have been doing this for ~3 weeks. I get up at 5:00AM, throw on some sweats, grab an umbrella (it is the Seattle area you know) and head out the door to walk for an hour.

After my walk I shower and get ready, having my breakfast about 20-30 minutes after my walk.

Seems to work for me and I am energized the rest of the day.