Srimad Bhagavatam Canto 04, Chapter 23, Text 05

SB 4.23.5

suska-parnasanah kvacit
ab-bhaksah katicit paksan
vayu-bhaksas tatah param
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In the tapo-vana, Maharaja Prthu sometimes ate the trunks and roots of trees, sometimes he ate fruit and dried leaves, and for some weeks he drank only water. Finally he lived simply by breathing air.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In Bhagavad-gita, yogis are advised to go to a secluded place in the forest and live alone in a sanctified spot there. By Prthu Maharaja’s behavior we can understand that when he went to the forest he did not eat any cooked food sent from the city by some devotees or disciples. As soon as one takes a vow to live in the forest, he must simply eat roots, tree trunks, fruits, dried leaves or whatever nature provides in that way. Prthu Maharaja strictly adopted these principles for living in the forest, and sometimes he ate nothing but dried leaves and drank nothing but a little water. Sometimes he lived on nothing but air, and sometimes he ate some fruit from the trees. In this way he lived in the forest and underwent severe austerity, especially in regards to eating. In other words, overeating is not at all recommended for one who wants to progress in spiritual life. Sri Rupa Gosvami also warns that too much eating and too much endeavor (atyaharah prayasas ca) are against the principles by which one can advance in spiritual life.
It is also notable that, according to Vedic injunction, to live in the forest is to live in the mode of complete goodness, whereas to live in the city is to live in the mode of passion, and to live in a brothel or drinking house is to live in the mode of ignorance. However, to live in a temple is to live in Vaikuntha, which is transcendental to all the modes of material nature. This Krsna consciousness movement affords one the opportunity to live in the temple of the Lord, which is as good as Vaikuntha. Consequently, a Krsna conscious person does not need to go to the forest and artificially try to imitate Maharaja Prthu or the great sages and munis who used to live in the forest.
Srila Rupa Gosvami, after retiring from his minister’s seat in the government, went to Vrndavana and lived beneath a tree, like Maharaja Prthu. Since then, many people have gone to Vrndavana to imitate Rupa Gosvami’s behavior. Instead of advancing in spiritual life, many have fallen into material habits and even in Vrndavana have become victims of illicit sex, gambling and intoxication. The Krsna consciousness movement has been introduced in the Western countries, but it is not possible for Westerners to go to the forest and practice the severe austerities which were ideally practiced by Prthu Maharaja or Rupa Gosvami. However, Westerners or anyone else can follow in the footsteps of Srila Bhaktisiddhanta Sarasvati Thakura by living in a temple, which is transcendental to residence in a forest, and to vow to accept krsna-prasada and nothing else, follow the regulative principles and chant sixteen rounds daily of the Hare Krsna mantra. In this way, one’s spiritual life will never be disturbed.
Srimad Bhagavatam Canto 04, Chapter 23, Text 04
Srimad Bhagavatam Canto 04, Chapter 23, Text 06