Kevin Costner hates the gym but is scared to quit it because he wants to look good for his wife and children.

The "Dances With Wolves" star, who turned 50 in January, admits he would love to stop doing exercises but is so worried about getting fat and losing his looks that he can't give up.

"I hate the gym. And I certainly don't like weights. But it's important for me to look good. So as much as I don't want to do this any more, it's vanity that keeps me going," he said.

The veteran actor recently gained 20 pounds (approx 9 kg) for his role as a drunken baseball player in new movie "The Upside of Anger", but believes if he let himself go permanently it would disappoint his family.

"I want to look good for my children and for my wife," he said.