There are a few that are proponants of the morning cardio idea. In its basic form (as an example only): One sleeps for approximated 8 yours, thus your in a fast for 8 hours approximently. This in returns results in your body being somewhat malnourished or in depleted state of immediate and necessary nutrients when cardio is done in the morning, and they say it taps into the fat stores because sugar is low (carb stores throughout the body), in addition to the benefit of burning calories----I put this in simplicity form.
I dont like the idea, personally. One could argue canabalism pretty fairly, especially WITH the addition of a deficit diet in 24 hours.
I like the idea of the afternoon or late morning WO. If you sleep for 8 hours, One is probably the weakest in the morning (Lack of water, lack of food, low blood sugar, possibly,, and many other negatives). But if you eat right in the morning (and have the night before), and then wait a few hours for digestion to take place and then ingest some water, etc. Then Morning WO would be okay in this sense, but not emmediately in the morning.
Just some brief Info.