PORTRUSH, Northern Ireland — Phil Mickelson, always a serial tinkerer with his golf game, has spent a lifetime reinventing himself.

Mickelson’s latest version of himself — on full display at Royal Portrush in advance of this week’s British Open — is 15 pounds lighter, with more bounce in his step and clarity in his soul after a recent retreat to Hawaii that included a six-day fast.

Also a part of the 49-year-old Mickelson’s recent reinvention has been his presence on social media. He joined Twitter last year and recently has taken to posting some rather hysterical videos called “Phireside with Phil” that provide some tongue-in-cheek funny inside stories and guests, including his mother.

The diet, Mickelson said, has been a product of him being “just not happy with the way I’ve been the last few months,” a span that has included struggles on the golf course. Since winning the Pebble Beach Pro-Am in February, Mickelson has missed six cuts, including each of his last two tournaments — the Travelers Championship and the 3M Open.

He finished 18th at the Masters, 71st in the PGA Championship at Bethpage Black and 52nd at the U.S. Open.

“I just haven’t been at my best mentally, physically, so I’m trying to control the things I can control, which is get physically better, let myself heal, give myself time to reset and recharge,” Mickelson said Tuesday in between shots during his morning practice round at Portrush. “I took 10 days and I didn’t eat for six. So many studies show the power of fasting and how your body will heal, so I tried to let it do that.

“The byproduct is losing weight. That wasn’t the intent. I don’t know if it’s going to help my golf or not, but I feel better. That’s all I can really control right now.”

Mickelson revealed that he “considered not playing this week,’’ but quelled those thoughts “because of my love for this tournament.”

“It’s kind of a spiritual place, a spiritual tournament,’’ he said. “If it was any other tournament, I’d take the week off.”

Mickelson, who’s always looking for an edge to improve himself and his performance on the golf course, said he’s “read for the last couple of years on a lot of stuff (about) fasting and diet.”

“One thing that resonated with me was a quote I read that said, ‘Everything you eat is either causing disease or helping your body fight disease,’” he said. “That kind of resonated with me. Now that I’ve reset, I’ve only put vegetables, fruits, nuts, seeds, along with a special (blend) of coffee (into my diet). I think coffee is one of the most powerful antioxidant foods that we eat. So I’ve been working on this special blend to help heal, help with mental clarity, putting a lot of cool ingredients in.”

The coffee drink Mickelson concocts — and consumes in a large black Yeti that he carried with him during his practice round Tuesday — has about six different ingredients.

“It has MCT (medium-chain triglyceride) oil for brain function, sea salt for overall energy, manuka honey for allergies and good bacteria, cinnamon for inflammation, collagen powder for recovery and almond milk,” Mickelson said.

Mickelson, who’s been known to love burgers from In ‘N Out and was an investor in the Five Guys burger chain, recently went to Hawaii with his family and consumed only coffee and water, did morning yoga on the beach and hiked.

“Then I came home and just kept it going,” he said. “The first day or two were difficult, but after three days, I didn’t crave food. I had plenty of energy.”

Mickelson, who conceded that “when I don’t play well, I don’t feel good about myself,” said since he’s made these changes, “I’m much calmer, less agitated, (have) better self-esteem (and) less anxiety.”

Mickelson has had an unexpected blast on social media, and said the “Phireside with Phil” chats that he posts on Twitter were partially inspired by the “Between Two Ferns’’ interview show with Zach Galifianakis.

“People want to hear the stories that you don’t ever hear from players, caddies and so forth,” he said. “I want it to be entertaining, but also insightful. I certainly think I’m funny, but I thought I was the only person who did.”

Mickelson, who revealed that he plans to shoot a couple of the videos this week from the Open, also has had some fun with people gawking at his calves, which have become a topic of conversation with players now wearing shorts in practice rounds.

Photos of Mickelson’s defined calves have gone viral on the Internet.

“This social media stuff has been more fun than I thought, and a more powerful tool than I thought,” he said. “I haven’t even been on a year, and I didn’t understand the power and ability to connect with people through this medium. I do hear about the calves. I have a lot of males show me their calves during the round and I’m like, ‘Dude, don’t. Just don’t.’”