Musannaf Ibn Abi Shayba 16:147

Abu Bakr narrated to us, he said: Hushaym narrated to us, from Yunus, from al-Hasan, from Abu Barzah, who said: We were on an expedition of ours, and we encountered some people from the polytheists. We drove them away from a basket of theirs, and we fell upon it. We began to eat from it. We used to hear during the Jahiliyyah that whoever eats bread becomes fat. So when we ate that bread, one of us began to look at his sides to see if he had become fat.