AM cardio was originally touted as best performed on an empty stomach. The reason being in a fasted state it is easier to burn fat rather than glycogen (however its not this simple) and also easier to reach a target pulse rate.
But, for a bodybuilder this activity might be catabolic. When an article ran in MM2K some years ago, drinking a litre of water was supposed to have some anti-catabolic effect. I am not sure, but drinking this much water on an empty stomach will make you puke it up and not great for pre-cardio.
The grapefruit diet where coffee and grapefruit was used for breakfast was your post cardio meal. The reason behind the grapefruit was some geezer found out that a component of grapefruit called 'narangenin' slows down the rate that the caffeine is converted to paraxanthine in the liver. Meaning you got some increased and longer thermogenic effect from the caffeine.
Drinking some juice from a can of tinned grapefruit (canned in nat juice not syrup) with mant fat burning stacks can help if you are using any, particularly methylxanthines (this is a group which includes caffeine).
AS for pre -workout, I think Dr. Lonnie Lowery said he used some whey in his coffee, pre cardio. Its enough to prevent catabolism (the body wanting to make glucose from certain amino acids in this case) during cardio. Its not just that you could ear after and re-gain and effects of lost muscle through catabolism, but cortisol levels would also be increased by fasted cardio. Amongst many other things, ascorbic acid helps with cortisol levels you could take some with a small pre cardio drink.
