Well, I was wondering is there anything wrong going to the gym with a full stomach, I just finished eating a big bowl of oatmeal with protein supplements, slice of bread w/ cheese and about 10 leaves of lettuces.
The only real problem I can see is that your body has to divert blood to your GI tract for digestion and therefore not as much is available to your muscles.
If you don't feel sluggish and it is the only way you can get in a workout and breakfast, than I think it is better to work out on a full stomach than not at all.
Maybe you could do something lighter, like a low carb protein shake before your workout and then get the heavier stuff into your system after your workout when your muscles need to replenish their glycogen and your body is primed to pull in the nutrients?