It has been reported in the Musnad of Imaam Ahmad that this breaks the fast:
“Two women were once fasting during the lifetime of Allaah’s Messenger and they almost died of thirst. This was mentioned to the Prophet (sallAllaahu ‘alayhi wa sallam) but he turned away from (allowing) them (to break the fast). Then they were mentioned to him again, so he called for them and ordered them to vomit, i.e. throw up, what was in their stomachs. So they both vomited and filled up a bowl with puss, blood and pieces of flesh. Then the Prophet (sallAllaahu ‘alayhi wa sallam) said: ‘These two fasted by refraining from what Allaah made lawful for them. but they broke their fast by doing what Allaah made unlawful for them. One of them sat with the other and they began to eat from the flesh of people.’”
What transpired with these two women in the presence of the Messenger of Allaah (sallAllaahu ‘alayhi wa sallam) from their vomiting vile and disgusting things – this was from the miracles that Allaah allowed to occur at the hand of His Messenger so that he could show the evil effects of backbiting to the people. Allaah says: “And do not backbite one another. Would one of you love to eat the flesh of his dead brother?” [Surah Al-Hujuraat: 12]
This hadeeth shows that backbiting breaks the fast. This is in the figurative sense, meaning it nullifies the reward of fasting.
Source : The least form of fasting is leaving off food and drink
What is Prohibited and Disliked for the one Fasting – by Shaikh Saalih Al-Fawzaan [Ittihaaf Ahlil-Eemaan bi-Duroos Shahri Ramadaan ,Al-Ibaanah.com]
This narration has been declared Dha’eef by Al Imaam Al-Albaani (rahimahullaah) in Silsilah adh-Dha’eefah (Volume 2, Page 10, Hadeeth no 519) & ‘Allaamah Ahmad Shaakir (rahimahullaah) in his Checking of Muhalla of Imaam Ibn Hazm (rahimahullaah) as mentioned by ash-Shaykh Jamaal al Haarithee (hafidhahullaah).
The link to the complete article is here :: http://vb.noor-alyaqeen.com/t21268/