That is exactly why everyone does it first thing in the morning before anything else. It's the perfect time to pull. Pulling dumps some bile and increases metabolism. Food in in the system fights against the most effective pulling could be.
Also I do this prior to dinner. Another great time to pull.
Yes, I know about Adreas' 4 minute thing. Many of us who love Andreas have decided to take the chance on the findings of Dr. Karach. I haven't noticed any major toxification from doing this for 20 minutes, and to this day, I feel like I'm still getting benefits.
That's my thoughts on the food issue, and it's up to you to make your own decision on the length of time to pull. You could do this in 5 - 4 minutes sessions, and that would be just fine!