Srimad-Bhagavatam: Canto 7 - Chapter 1 - Verse 19
नैतत्पूर्वर्षयश्चक्रुर्न करिष्यन्ति चापरे ।निरम्बुर्धारयेत्प्राणान् को वै दिव्यसमा: शतम् ॥ १९ ॥
naitat pūrvarṣayaś cakrurna kariṣyanti cāparenirambur dhārayet prāṇānko vai divya-samāḥ śatam
Even saintly persons like Bhṛgu, born previously, could not perform such severe austerities, nor will anyone in the future be able to do so. Who within these three worlds can sustain his life without even drinking water for one hundred celestial years?
It appears that even if a yogī does not drink a drop of water, he can live for many, many years by the yogic process, though his outer body be eaten by ants and moths.