It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) would spend several consecutive nights with an empty stomach, such that the members of his household would not find dinner for the night, and most often, the bread they had to eat was made of barley.
Hadith Referenceمسند احمد / ومن مسند بني هاشم / 2303