A man used to eat a great deal. Then he embraced Islam and began eating little. This was mentioned to the Prophet ﷺ, who said, "The believer eats with one stomach, while the disbeliever eats with seven stomachs."
أن رجلا كان يأكل أكلا كثيرا، فأسلم، فكان يأكل أكلا قليلا، فذكر ذلك للنبي ﷺ فقال: إن المؤمن يأكل في معى واحد، والكافر يأكل في سبعة أمعاء.
Bukhari narrated it in the Book of Foods (5397) from Sulayman bin Harb, who said, Shubah narrated to us, from Adi bin Thabit, from Abu Hazim, from Abu Hurairah, and he mentioned it.