A man used to eat much, but when he embraced Islam, he started eating less. That was mentioned to the Prophet ﷺ who then said, "A believer eats in one intestine (is satisfied with a little food) and a Kafir eats in seven intestines (eats much). " (Using translation from Bukhārī 5397)   

جَاءَ كَافِرٌ إِلَى النَّبِيِّ ﷺ فَأَسْلَمَ فَجَعَلَ يَأْكُلُ قَلِيلًا وَكَانَ قَبْلَ ذَلِكَ يَأْكُلُ كَثِيرًا فَذَكَرَ ذَلِكَ لِلنَّبِيِّ ﷺ فَقَالَ «إِنَّ الْكَافِرَ يَأْكُلُ فِي سَبْعَةِ أَمْعَاءٍ وَالْمُؤْمِنُ يَأْكُلُ فِي مَعِيٍّ وَاحِدٍ»