SB 7.3.19

naitat pūrvarṣayaś cakrur
 na kariṣyanti cāpare
nirambur dhārayet prāṇān
 ko vai divya-samāḥ śatam
Word for word: 
na — not; etat — this; pūrva-ṛṣayaḥ — the sages before you, such as Bhṛgu; cakruḥ — executed; na — nor; kariṣyanti — will execute; ca — also; apare — others; nirambuḥ — without drinking water; dhārayet — can sustain; prāṇān — the life air; kaḥ — who; vai — indeed; divya-samāḥ — celestial years; śatam — one hundred.
Translation: 
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?
Purport: 

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.