A person in Kṛṣṇa consciousness does not eat anything which is not first offered to Kṛṣṇa. Therefore, only the Kṛṣṇa 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.
Bhagavad-gītā 6.16, Purport (Excerpt)