The 42-year-old actor's wife is pregnant with their third child and McConaughey makes sure to cook for her at every chance he gets, reported Us magazine.
"I'm playing a guy who is sick in my new movie so I need to lose muscle mass. I am on a high protein, low carbohydrate diet. I eat small amounts, only five ounces. But I'm doing a lot of cooking for Camila. She's loves a good steak so I've been making rib-eye for her when I can," McConaughey said.
The actor also said that he and Alves try to make sure their kids Levi, four and Vida, two, aren't spoiled by teaching them to give back.
"We're doing little things. We ask them which toy from Santa they want to give away to people in need," he added.