The 28-year-old shut down his season in October to recuperate from a persistent rib problem and has spent the time since reassessing his lifestyle and approach to the game.
The former world No.1 has not won a tournament since clinching the US season-ending Tour Championship in September 2016 and he won the last of his four majors in 2014.
McIlroy was diagnosed with a minor heart irregularity, found during a routine health check in April, but says "basically, it's nothing." A scan showed a thickening in the heart wall, but his doctors said it is "just something you have to keep on top of."
In need of a 'sabbatical'
However, McIlroy has undergone blood profiles and worked with a dietician, monitoring his salt intake and upping his fish oil intake with six tablets a day.
He has, he says, become a "bit of a pain in the backside" for waiters by continually ordering food cooked in specific ways or without oil or butter.
"[It's] just be a little more careful about what I'm putting into my body and obviously that can dictate energy levels and all that stuff," a trim-looking McIlroy told reporters ahead of the Abu Dhabi HSBC Championship.
He added: "I've actually put on about two kilos since October. But obviously that's two good kilos. I've lost a bit of fat and put on a bit of muscle."
McIlroy also got married in 2017, and spent some of his three months off driving around Italy with his new wife Erica in a 1950s Mercedes convertible. He also spent four-and-a-half weeks in Dubai, tentatively rehabilitating his golf game.
He then went back to the US for Thanksgiving, visited his native Belfast and New York over the Christmas break, celebrated New Year at Ashford Castle in County Mayo, Ireland, and went out to Abu Dhabi in early January to practice in earnest.
"I felt like I needed it physically and mentally," he told reporters. "I've been out here (on tour) for 10 years and it just felt like it was a little bit of a sabbatical."
'No better feeling'
McIlroy did score six top 10s in 14 PGA Tour events last year, including seventh at the Masters and fourth at the Open, but his win drought is a major talking point as Dustin Johnson, Jordan Spieth and Justin Thomas have taken a stranglehold at the head of the game.
Now that he is fit again, McIIroy has committed to a strenuous run of eight tournaments before the Masters in April, the first major of the year, when he can become one of only six players to clinch a career grand slam of all four major titles.
But he is adamant that Masters success -- he has a best finish of fourth in 2015 -- is not dependent on winning a title or two before he reaches Augusta.
"I don't need to but I'd love to," he said, adding he was planning to arrive earlier at tournaments -- on the Monday of that week -- to give himself more preparation time than in the past.
"I don't think there's any better feeling than winning a golf tournament. But I don't feel like it's that far away," he said.