Image: astanhope [Flickr]
From astanhope's Flickr set on Thailand, here's a statue of the Fasting Buddha at the Wat U-Mong temple in Chiang Mai, Thailand.
The short version of the story goes like this: After the young prince Siddhartha Gautama left his palace to search for enlightenment, he lived as an ascetic for six years. The emaciated Siddharta finally attained enlightenment and became Buddha (The Enlightened One) when he discovered the Four Noble Truths [wiki]. The statue above depicts this part of his life.
If you're only familiar with the fat Buddha, here's another fact for you: it is not Siddharta at all. There are 28 Buddhas, of which Siddharta was one.