An empty stomach has one problem; A full stomach has a 100 problems:

Diet and Yoga- Wisdom from ancient texts

1) Obstacles to the flow of Prana

Patanjali, in yoga sutra 4.3 says,

Just as a farmer does not carry water from the river to the fields but removes the obstacles that prevent the water to flow and creates bunds, so too do the yogic practices remove the obstruction to the flow of consciousness

Fig. 1: Bunds in a field

It is so with yoga practice as well, whether one is practicing asanas, pranayama or dhyana (meditation); the ability to attain siddhi (mastery) in one's yoga practice depends on the ability to tap and harness the prana in our body. Everything we do in the asana practice -Ujjayi breath, bandhas etc. harness the prana. The flow of prana makes the body malleable, fit for tapping into higher states of consciousness. There are many things that block the flow of prana, the chief among them is a bad diet. This is why mitahara (light, sattvic diet) is recommended for the yogi in all yogic texts that go into some details on various yogic practices.

2) The various yoga texts on Mitahara (moderate diet)

Swami Sivananda of Rishikesh pointed out, “Heavy food leads to a dull, tamasic state that induces sleep. There is a general misconception that a large quantity of food is needed for health and strength. Much depends on the power of assimilation. Most diseases are due to an unwholesome diet and overeating”.

The hatha yoga pradipika says,

The Gheranda samhita goes even further. It puts a section on Kriyas (cleansing techniques) before the section on asanas. It is true that without proper elimination one cannot tap into the prana. I had described Indra Devi’s initial puzzlement and later thankfulness when she started her tutelage under T. Krishnamacharya in a previous article. According to the Gheranda Samhita,

3) Moola Bandha and measure of a full stomach

Pattabi Jois, the founder of the "Ashtanga Yoga" tradition, would often say that the Moola bandha or the root lock should always be "ON" except during three occasions - eating, using the restroom and while sleeping. Moola Bandha is the upward lifting of the perennial floor (the region between the anus and the genitals) which gives a feeling of lightness and an upward flow of prana. Asana practitioners use this technique to induce a a feeling of levitation. While it is difficult for most of us to do this all the time, it can be used as a check to see if one has overeaten.

4) Conclusion

Therefore abstaining from overeating and sticking to a light diet is essential for a yogi who wants to access the prana to tap into higher consciousness. It should be done as an act of tapas as described in the previous article. For after all, as Sadhguru says,

An empty stomach has one problem;

A full stomach has a 100 problems