How much will you spend on lunch today? $5? $10? $15? What if you could only spend $1.50 — and what if that was the only money you had to spend on food all day?

The Global Poverty Project is challenging people to try to live on $1.50 of food a day from April 29 to May 3 as part of the group's "Live Below the Line" initiative. The annual event, first held in 2009, is designed to give participants a better understanding of "the daily obstacles faced by 1.4 billion people trapped in the cycle of extreme poverty."

The $1.50 figure isn't arbitrary. It's based on figures the World Bank came up with to categorize people who live in "extreme poverty" in some of the world's poorest countries. In those nations, the $1.50 covers not just food but also housing, transportation, health care and education. The World Bank last calculated this "extreme poverty line" in 2005, when it placed the number at $1.25 a day; the Global Poverty Center has updated it to reflect inflation over the past eight years.

Live Below the Line has support from a number of celebrities, including "Entourage" actress Debi Mazar, who is pledging to live on $1.50 a day for the week, and "Wolverine" star Hugh Jackman, who recorded this PSA:

Hugh Evans, co-founder and CEO of the Global Poverty Project, recently appeared on MSNBC's "Morning Joe" to discuss the initiative. As he described it, "it's kind of like running a marathon. Every day you do it you get people to sponsor you and the money you raise goes to support incredible organizations like the World Food Program, who are on the cutting edge to end extreme poverty in the world." The people who sign up for the Live Below the Line Challenge can choose to raise money for any of a dozen partner organizations dedicated to hunger relief,including Unicef, the Eastern Congo Initiative, World Food Program USA and Opportunity International. Last year participants raised an average of $221 each.

You can see more of Evans' appearance on "Morning Joe" below, and follow the "Live Below the Line" initiative on Facebook.