It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him); he said: A man from the People of the Book came to the Messenger of Allah (peace and blessings be upon him) and said: "O Abu al-Qasim! You claim that the people of Paradise will eat and drink, yet whoever eats and drinks also has a need to relieve himself?" The Messenger of Allah (peace and blessings be upon him) said: "The need of each of them is sweat that will flow from his skin, and then his stomach will become slender."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4985