Magician David Blaine – who once went without food for 44 days while suspended above London's River Thames – phoned Farrow with some tips on how to prepare. "He told me to drink 4 liters of water. Do you know how much water that is?"," Farrow wrote on her blog. "He said after 6 days I won't feel hunger."
In a video posted Thursday to her blog, Farrow explains that she's weak after four days of fasting and spending lots of time in her bedroom at her Bridgewater, Conn., home. "Being hungry all the time, which I am, just brings my mind to all the people who are starving," she says.
Last week Farrow told PEOPLE she hopes to stop eating for three weeks to show support for Darfur, where one million people are at risk of starvation after the Sudanese government expelled 13 aid agencies in March. After consulting a doctor, she gained 9 lbs. in preparation for the fast and plans to have her blood tested after two weeks. "If there is organ damage, I will have to stop," she told PEOPLE.