The 43-year-old, who is losing weight for a role in the movie "The Dallas Buyer's Club", is at his lowest point, weight wise, reported Radar online.
McConaughey has lost 30 lbs and gained a moustache for the role. In the movie, he plays a mid-1980s AIDS patient who seeks out experimental HIV drugs to prolong his life.
"Matthew starts shooting this weekend, so he's at his absolute lowest weight. In a month, he'll begin to put it back on," a source said.
Te actor has flown to New Orleans to begin filming the new movie in which he plays Ron Woodruff.
Earlier the 'Lincoln Lawyer' star admitted he found losing the extreme amount of weight to be a huge mental challenge.
"I'm playing a guy who was sick and would have loved to have been healthier but wasn't. For me, it's more of a mental thing than a physical thing," he had said.
