Brian Austin Green has started "losing" his sex drive as he's got older.

The 53-year-old actor - who has Kassius, 24, with ex-girlfriend Vanessa Marcil, Noah, 13, Bodhi, 12, and nine-year-old Journey with former wife Megan Fox and Zane, four, with fiancée Sharna Burgess - believes it is very normal for men's desire to have sex to decrease as a result of a "chemical thing" within their bodies.

Speaking on his I Do, Pt. 2 podcast, Brian read out a listener question before giving a candid answer.

He said: "As men age, do you notice that your sex drive is lowering?

"Sure. Absolutely. Of course.

"That is a chemical thing. That is testosterone, and that is what men, as they age, start naturally losing. You can take supplements and you can, you know, go the opposite direction. But to me, honestly, absolutely -- sex drive lowers. There's no way to avoid that."

The Beverly Hills, 90210 actor noted that as his physical desires have waned, emotional connection has become more important in his relationship with 41-year-old Sharna.

He said: "It's not just the physical act the same way. There's emotion to it too.

"My fiancée now is...we started very early with that understanding of we'll talk about everything. So there is no unknown if she's feeling a certain way or I'm feeling a certain way."

Brian's co-host, Bob Guiney, 55, agreed but admitted he needs to be mindful of the needs of his 42-year-old wife Jessica Canyon.

He said: "I am married to someone younger. Part of me making sure that I am there for her in the ways that she needs me to be as well, you can't just sit on the couch all the time and expect to be the guy that's ready to go."

The Zombie Plane actor recently admitted on the podcast that the end of his marriage to Megan made him learn to build his relationships around friendship instead of physical attraction.

He said: "Until Sharna [Burgess], my ex and I were together for almost 15 years. We were married for almost 10 years and I led with physical attraction.

"First, I'd be physically attracted to somebody and then sort of build a relationship around that.

"I was divorced, which I didn't expect. I had three kids. I was a single parent.

"And I knew that I didn't want to repeat things that I had done. So I went through all sorts of therapy and all sorts of things to really figure out what it was that I brought into a relationship that was just toxic and wasn't good and wasn't helping the relationship at all."

After working on himself, Brian realised he needed to "be friends with someone first" before pursuing a romantic relationship and adopted this "different" approach with Sharna.

He said: "I think when you started from a place of a genuine connection with someone, then you're not so concerned about whether they are truly into you or not, because you guys are already speaking to each other in a very transparent way."