Tim McGraw lost 40lbs because he wants to be alive for his future grandchildren.

Tim McGraw

Tim McGraw

The 52-year-old star was inspired to undergo a dramatic change when his wife Faith Hill told him to "get over [himself]" and was further driven to overhaul his lifestyle when his daughter Gracie, who was "11 or 12 at the time", was shocked when she saw a trailer for his 2008 movie 'Four Christmases' on a giant cinema screen.

Of Faith's comment, he admitted: "That's a big one..."There's a certain amount of writing it off a little bit because it's part of the syntax of a relationship. And when your kids [say it], kids are so honest...

"My daughter looked over at me and said, 'Jeez, Dad, you need to do something.'

"It got me thinking, you know, I want to be around. I want to be around to see my grandkids. And I want to be around to see what these kids do with their lives, you know?"

The 'Humble and Kind' singer - who, as well as Gracie, now 22, also has Maggie, 21, and Audrey, 18, with Faith - thinks some of his weight gain was due to the "musician's lifestyle".

He explained to 'Entertainment Tonight': "Everything was good. My career was good. I was just pretty lazy in my life."

Tim urged his fans to "take that first step" and start with something simple and build up to more physical activity as the weeks go on.

He said: "I didn't start with gym memberships. I didn't start with trainers. I didn't start with any of those things. I started by walking every day.

"The more I walked, the more I wanted to do and the more I wanted to do bodyweight stuff. So, that gym stuff wasn't part of my program for a while...

"Take that first step. Just say, 'I'm gonna walk 10 minutes at 7 a.m. or 8 a.m. or 9 a.m.,' whatever your wake up time is. 'I'm gonna walk 10 minutes today.' You do that for 10 weeks and I guarantee it'll lead to something else."