"As soon as Cherry told me she was pregnant, life shifted, in terms of work and health and what I was putting into my body, be it food or alcohol," he told BBC Radio 1's Greg James.
"I started exercising more and my routine became a bit more healthy."
The star also changed his work habits, working "nine to five" instead of finishing recording sessions at 2am.
"It actually freaks out producers," he said. "I was in Los Angeles working with these producers that usually start working at 6pm and finish at 6am with people like Post Malone and Dua [Lipa].
"I was like, 'Yeah, we're starting at nine'. And they were like, 'What?'
"But I do find you get more done. There's less faffing."
Sheeran and wife Cherry Seaborn announced the birth of their first child, Lyra Antarctica Seaborn Sheeran, in August, telling fans they were "completely in love".
The pop star later revealed the newborn was "not my biggest fan" and "just cries" when he sings his new songs to her.
Speaking to Apple Music's Zane Lowe, he also said becoming a father had changed his relationship with his parents.
"It was amazing before, but now it's just like there's this eternal gratefulness and respect of being like, I know what they went through and I'm still going through it.
"And also, the other thing is, no-one knows what they're doing. I see people and I'm like, 'Oh my God, that guy's the best dad in the world'. But he started off like me, like not knowing anything.
"I'm learning day by day. So I think it's amazing,"