Matthew McConaughey is slowly gaining back the 50 pounds he lost while preparing to play a man with AIDS in "The Dallas Buyers Cub," the New York Post said.

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"Matthew is on a special diet to put on weight," a source told the newspaper during the weekend, adding he is not binging on high-calorie foods in an effort to pack on the pounds fast.

"He's eating fish because it's healthier."

McConaughey is known for his athletic build but made headlines in recent months because of his drastic weight loss and gaunt appearance.

He has since wrapped production on "The Dallas Buyers Club," which is due out in theaters later this year.