The father of Zayd bin Aslam (may Allah have mercy on him) says: A year came upon the Muslims in which the price of ghee rose, and Sayyiduna Umar (may Allah be pleased with him) would eat olive oil, which made his stomach rumble. In the narration of Yahya: Sayyiduna Umar (may Allah be pleased with him) used to eat ghee; when it became scarce, he said: I will not eat it until the people eat it. So he used to eat oil, which made his stomach rumble. In the narration of Ibn Mukram: Sayyiduna Umar (may Allah be pleased with him) addressed his stomach and said: Rumble as much as you like; by Allah, I will not eat ghee until the people eat it. Then he said to me: Take away its heat (harshness) with fire. So I used to cook it for him and he would eat it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17909