The 'Dallas Buyers Club' star revealed he called the two-time Oscar winner for advice before slimming down to play real-life AIDS victim Ron Woodroof in the new film.
He told People.com: "I actually called Tom and had a great conversation with him about what he learned about losing weight for 'Philadelphia' and 'Cast Away.' And I consulted a nutritionist about the best way to do this."
The 43-year-old actor was 185 lbs. before the drama and was determined to shock people with his transformation.
He said: "I was going around and people were going, 'Hey, are you feeling all right?' But then I hit 135 lbs. I ran into somebody and they didn't just ask if I was all right, they said, 'My God, we need to get you some help.' And I thought, 'There we go. That's the perfect spot.' "
Matthew, who has two sons, Levi, five, and Livingston, eight months, and daughter Vida, three, with his wife Camila, isn't worried that the weight loss will affect his health in the long run.
He said: "I fed myself good food, just not much of it. I found through this journey that the human body is much more resilient than we give it credit for.
"Somebody told me they heard a story about how I didn't have any energy on set, but I was kind of uncontainable with energy. All the acuity, energy and power I lost from the neck down transferred to the neck up."