In plain words
Yoga is not for one who eats too much, nor for one who eats too little; not for one who sleeps excessively, nor for one who is always awake, Arjuna.
Word for word
Yoga is not for one who eats too much, nor for one who altogether does not eat, and not for one given to too much sleep, nor indeed for one who keeps awake, O Arjuna.
नात्यश्नतस्तु योगोऽस्ति न चैकान्तमनश्नतःन चातिस्वप्नशीलस्य जाग्रतो नैव चार्जुन
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
इदानीं योगिनः आहारादिनियम उच्यते —
न अत्यश्नतः आत्मसंमितमन्नपरिमाणमतीत्याश्नतः अत्यश्नतः न योगः अस्ति । न च एकान्तम् अनश्नतः योगः अस्ति । ‘यदु ह वा आत्मसंमितमन्नं तदवति तन्न हिनस्ति यद्भूयो हिनस्ति तद्यत् कनीयोऽन्नं न तदवति’(श. ब्रा. ?) इति श्रुतेः । तस्मात् योगी न आत्मसंमितात् अन्नात् अधिकं न्यूनं वा अश्नीयात् । अथवा, योगिनः योगशास्त्रे परिपठीतात् अन्नपरिमाणात् अतिमात्रमश्नतः योगो नास्ति । उक्तं हि — ‘अर्धं सव्यञ्जनान्नस्य तृतीयमुदकस्य च । वायोः सञ्चरणार्थं तु चतुर्थमवशेषयेत्’(?) इत्यादिपरिमाणम् । तथा — न च अतिस्वप्नशीलस्य योगो भवति नैव च अतिमात्रं जाग्रतो भवति च अर्जुन ॥ १६ ॥
In plain words
Now, the rules about food and daily habits for the yogī —
Overeat—take in more food than your own body actually needs—and yoga isn't possible for you. Starve yourself entirely, and it isn't possible either. As the scripture says: ‘Food measured to one's own need protects and never harms; too much harms; too little doesn't protect.’ So the yogī should eat neither more nor less than what suits himself. Or, put another way: eating more than the measure the yoga texts prescribe also makes yoga impossible. As it is said: ‘Fill half the stomach with food and its accompaniments, a third with water, and leave the last quarter free for the breath to move.’ In just the same way, Arjuna, yoga isn't possible for someone who sleeps too much—nor for someone who stays awake too much either.
Close to the Sanskrit
Now the regulation of food and so on for the yogī is stated —
For one who overeats—i.e. eats, exceeding the measure of food proportioned to himself—yoga does not exist for him. Nor, for one who abstains entirely, does yoga exist. As the scripture says: ‘Whatever food is proportioned to oneself indeed protects him; it does not harm him; whatever food is more harms him; whatever food is too little does not protect him.’ Therefore the yogī should not eat more or less than the food proportioned to himself. Alternatively, for the yogī who eats in excess of the measure of food taught in the yoga treatise, yoga is not possible. For it has indeed been said: ‘Half the stomach with food and its condiments, a third with water, but one should leave a fourth for the circulation of air’—such is the measure, and so on. Likewise, for one habitually given to excessive sleep, yoga is not possible, nor indeed for one who stays excessively awake, O Arjuna.
▸Gītā Vāhini
“బావా, లెమ్ము! ధ్యానయోగమును అభ్యసించుము; క్రమము తప్పక, కాలము మార్చక, స్థానమును వీడక, మనస్సును అరికట్టుటకు పూనుకో. ఈ యోగమునకు క్రమము ప్రధాన అంగము; దానిని అతి జాగ్రత్తగా పాటించవలెను. ఇష్టమొచ్చినట్లంతయూ పద్ధతులు మార్చకూడదు. అది ప్రమాదమునకు గురియగును. అతిగా తిని ఆయాస పడువానికీ, తిండి తినక దేహమును కృశింపజేయువానికీ, అతిగా నిద్రించువానికీ, అసలే నిద్రలేక నిరంతరము మెలుకవతో నుండు వానికీ, అనుకూలమును పట్టి ధ్యానమును ఆచరించువానికీ (అనగా నేడు ఏ పనీ లేదని ఆనాడు ఎక్కువ కాలము, రేపు అతి పని కలదని ఆనాడు ఏదో శాస్త్రముగా జరుపువాడు), కామక్రోధాది షడ్గుణములను విచ్చలవిడిగా ఉపయోగించువానికీ, తల్లిదండ్రుల యొక్క హృదయములను హింసించువానికీ, మాతృదేవి హృదయమును సంతృప్తి చేయనివానికీ, వీటన్నిటి కంటే అతి ముఖ్యమైనది భగవంతునియందు గానీ లేక ఎవరిని గురువుగా, దైవముగా భావించి హృదయము అర్పితము చేసితివో, అట్టి వారలపై సంశయములు, అవిశ్వాసములు ప్రదర్శించువానికీ, ఎన్ని యుగములు ధ్యానము చేసినా ఫలసిద్ధి కాజాలదు.”
In plain words
“Brother-in-law, arise! Practise Dhyāna Yoga. Without breaking the order, without changing the time, without leaving the place, set yourself to restrain the Manas. For this yoga, regularity is the chief limb, and it must be kept very carefully. Methods must not be changed just as one pleases; that will lead into danger. For him who eats too much and grows weary; for him who does not eat and wastes the body; for him who sleeps too much; for him who stays constantly awake without any sleep; for him who practises dhyāna by convenience (that is, the one who, because there is no work today, sits for a long time that day, and because there is too much work tomorrow, gets it done that day as a mere formality); for him who indulges the six qualities, kāma, krodha and the rest, without restraint; for him who torments the hearts of his parents; for him who does not content the heart of his mother, a goddess to him; and, most important of all, for him who shows doubts and distrust towards God, or towards those whom you have regarded as guru and as God and to whom you have made an offering of your heart — however many yugas he may do dhyāna, the fruit can never be attained.”