support for my answer – “Well, it is safe in the sense that nothing bad will happen, but it isn’t optimal. Having food in your stomach while exercising may make you feel uncomfortable, especially if you are running. It also makes it harder for your body to digest.” source
But I believe Dr. Mirkin said it best “Food stays in your stomach for a while after you eat because it can’t leave until it’s turned into liquid. As long as food is in the stomach, your stomach muscle must squeeze to turn it into a liquid soup. Active muscles need huge amounts of oxygen from the blood that flows to them.
When food is in your stomach during exercise, your heart has to pump blood to both the exercising muscles and those in the stomach. If your heart is not strong enough to supply blood to both, it stops pumping blood to the stomach muscles, which lack oxygen, accumulate lactic acid and start to hurt. ”