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 the generation among whom I was sent, then those who come after them" - he said it three times - Allah knows best whether he mentioned the third 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 / 15619