It is narrated from Sayyiduna Imran bin Husayn (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The best of my Ummah are those among whom I was sent, then those who come after them, then those who come after them - Allah knows best whether the narrator mentioned the third generation or not - then there will arise people who will give testimony though their testimony is not sought, who will make vows but not fulfil them, who will betray though they are not entrusted, and obesity will become widespread among them."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15618