nāty-aśnatas tu yogo ’sti
na caikāntam anaśnataḥ
na cāti-svapna-śīlasya
jāgrato naiva cārjuna

Translation of Bhagavad Gita 6.16

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 Sri A.C. Bhaktivedanta Swami Prabhupada of Gaudiya Sampradaya:

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 Vishvanatha Chakravarthi Thakur of Gaudiya Sampradaya:

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.

Commentary by Sri Ramanuja of Sri Sampradaya:

6.16 Over-eating and excessive fasting are opposed to Yoga. So also are excessive recreation and non-recreation, too much of sleep and too much of vigil. So too, are overwork and idleness.

Commentary by Sri Sridhara Swami of Rudra Sampradaya:

The regulations regarding the eating of food and the regimen of sleep that are to be followed by those practising yoga or the science of the individual consciousness attaining communion with the ultimate consciousness are now being given by Lord Krishna. By not following these injunctions it is not possible to even commence practising any form of yoga.

Commentary by Sri Madhvacharya of Brahma Sampradaya:

Abstention from performing regulatory fasting such as Ekadasi which is the 11th day of the waxing or waning moon is sanctioned only for the weak and invalid. In the Narada Purana it states: That one who is strong having given up sleep, food, fear, lethargy and actions, meditates within on the Supreme Lord Krishna or His authorised incarnations with eyes half-closed focused on the tip of the nose or the space between the eyebrows attains equanimity of mind.

Commentary by Sri Keshava Kashmiri of Kumara Sampradaya:

After describing the results of meditation Lord Krishna gives the regulations regarding the eating of food and the regimen of sleep habits. One who eats like a glutton or sleeps like a sloth as well as one who fasts too much and sleeps to little are never qualified to practise yoga or the science of the individual consciousness attaining communion with the ultimate consciousness. In regard to food it is described by Pantajali that the stomach should be filled one-half with food, one-quarter with liquid and one-quarter should be kept free for the movement of air.

Commentary by Sri Adi Shankaracharya of Advaita Sampradaya:

6.16 (Tu, but) O Arjuna, Yoga na asti, is not; atiasnatah, for one who eats too much, for one who eats food more than his capacity; na ca, nor is Yoga; anasnatah, for one who does not eat; ekantam, at all. This accords with the Vedic text, ‘As is well known, if one eats that much food which is within one’s capacity, then it sustains him, it does not hurt him; that which is more, it harms him; that which is less, it does not sustain him’ (Sa. Br.; Bo. Sm. 2.7.22). Therefore, a yogi should not eat food more or less than what is suitable for him. Or the meaning is that Yoga is not for one who eats more food than what is prescribed for a yogi in the scriptures on Yoga. Indeed, the quantity has been mentioned in, ‘One half of the stomach is to be filled with food including curries; the third quarter is to be filled with water; but the fourth quarter is to be left for the movement of air,’ etc. Similarly, Yoga is not for ati svapna-silasya, one who habitually sleeps too long; and Yoga is na eva, surely not; jagratah, for one who keeps awake too long. How, again, does Yoga become possibel? This is being stated:

Commentary by Sri Abhinavagupta of Kaula Tantra Sampradaya:

6.16-17 Yogosti etc. Yuktahara etc. For foods : for sense-objects that are being brought [by sense-organs]. Effort : activity for enjoying [them]. Its appropriateness is neither to have unlimited indulgence, nor to have unlimited abstention. The same is in all cases. The rest [of the text] is clear. On the authority of the Sage [Vyasa], the form jagaratah etc. [may be viewed correct] as those in the Vedic literature. The same is in other similar instances also.

Sanskrit Shloka Without Transliteration Marks:

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

Sanskrit to English Word for Word Meanings:

na — never; ati — too much; aśnataḥ — of one who eats; tu — but; yogaḥ — linking with the Supreme; asti — there is; na — nor; ca — also; ekāntam — overly; anaśnataḥ — abstaining from eating; na — nor; ca — also; ati — too much; svapna-śīlasya — of one who sleeps; jāgrataḥ — or one who keeps night watch too much; na — not; eva — ever; ca — and; arjuna — O Arjuna.