The following is a very good and important question:

How long should I wait after eating before practicing asana?

Just as you don’t eat right before going for a run, it is important to have the stomach (and preferably the bowels) as empty as possible before performing yogasana. Not only will this precaution help reduce discomfort in the practice, but it protects healthy and wellbeing. Asana can work far deeper than the body’s surface. Many poses provided a self-massage to the internal organs, such as ardha matsyendrasana (seated spinal twist) and other twisting poses. Inversions, such as sirsana (headstand) and sarvangasana (shoulderstand), powerfully affect the digestive system.

yum.

So how much time should I allow between a meal and practice?
In general, it is suggested to wait 4 hours after a large meal and 1 to 2 hours after a very light meal.
B.K.S. Iyengar states in Light on Yoga:

“Asana should preferably be done on an empty stomach. If this is difficult, a cup of tea or coffee, cocoa or milk may be taken before doing them. They may be practiced without discomfort one hour after a very light meal. Allow at least four hours to elapse after a heavy meal before starting the practice. Food may be taken half an hour after completing the asana.”

Waiting to eat for some times after practice is important as well. This helps the entire body receive the full benefits of the asana.

If you practice in the morning on an entirely empty stomach and experience light-headedness, try having a light snack, such as a banana, nuts, or other fruits, an hour or two before.

Green and young coconut water is very energizing and nutritious. It can be enjoyed a little before practice.
If fresh coconuts might not be available where you live, try packaged Zico or Vitacoco.

Some bread I baked at my old apartment in Astoria, NY. It’s best to wait a few hours before practicing after eating something like this.