Text 16

naty-asnatas ’tu yogo ’sti
na caikantam anasnatah
na cati-svapna-silasya
jagrato naiva carjuna

Translation

There is no possibility of one’s becoming a yogi, O Arjuna, if one eats too much or eats too little, sleeps too much or does not sleep enough. 

Commentary by Srila Prabhupada 

Regulation of diet and sleep is recommended herein for the yogis. Too much eating means eating more than is required to keep the body and soul together. There is no need for men to eat animals, because there is an ample supply of grains, vegetables, fruits and milk. Such simple foodstuff is considered to be in the mode of goodness according to the Bhagavad-gita. Animal food is for those in the mode of ignorance. Therefore, those who indulge in animal food, drinking, smoking and eating food which is not first offered to Krishna will suffer sinful reactions because of eating only polluted things. Bhunjate te tv agham papa ye pacanty atma-karanat. Anyone who eats for sense pleasure, or cooks for himself, not offering his food to Krishna, eats only sin. One who eats sin and eats more than is allotted to him cannot execute perfect yoga. It is best that one eat only the remnants of foodstuff offered to Krishna. A person in Krishna consciousness does not eat anything which is not first offered to Krishna. Therefore, only the Krishna conscious person can attain perfection in yoga practice. Nor can one who artificially abstains from eating, manufacturing his own personal process of fasting, practice yoga. The Krishna conscious person observes fasting as it is recommended in the scriptures. He does not fast or eat more than is required, and he is thus competent to perform yoga practice. One who eats more than required will dream very much while sleeping, and he must consequently sleep more than is required. One should not sleep more than six hours daily. One who sleeps more than six hours out of twenty-four is certainly influenced by the mode of ignorance. A person in the mode of ignorance is lazy and prone to sleep a great deal. Such a person cannot perform yoga.

Commentary by Sri Visvanatha Cakravarti Thakur

Two verses describe the rules for making practice of yoga steady. One who eats too much is not a yogi. It is said,

purayed asanenardham trtiyam udakena tu
vayoh sancaranartham tu caturtham avasesayet

One should fill the stomach half with food, one quarter with water, and one quarter remaining for the movement of air.