"He [the Dalai Lama] was feeling good yesterday," Chhime Chhoekyapa, a senior aide to the Dalai Lama, said.
"He is feeling better today, he started fasting from this morning and he will continue 'till evening. The doctors say that there is nothing to worry about."
During the fast, which was organised by the Tibetan Solidarity Committee, a statement was issued by the Tibetan government-in-exile calling on Tibetans to "put concerted non-violent efforts to bring a natural end to the torture and persecution in Tibet".
"This is a very solemn moment for all the Tibetans," said Tenzin Tsundue, a Tibetan poet and activist.
"This is a time to reflect on how we did this year for freedom and a moment to pause and think for ourselves in these trying times of our history."
The Tibetans' situation has been highlighted this year following protests and lobbying during the Olympic Games in Beijing earlier in August.
China's crackdown on protests in Tibet in March drew widespread condemnation from from around the world ahead of the Games.