Phil Mickelson said he hasn't "felt good about myself and the way I’ve been playing." (Jon Super/AP)

Phil Mickelson shared the drastic dieting measures he has taken to improve his golf game Sunday, telling his followers on social media that he had lost 15 pounds over a 10-day period and fasted for six days to attempt to get back to his peak performance before the British Open.

“I haven’t posted anything because I haven’t felt good about myself and the way I’ve been playing,” Mickelson said in the video posted to his Twitter and Instagram accounts. “And so I haven’t done anything or wanted to be in public. The last 10 days I’ve done what I call a hard reset to change and try to make things better.”

The five-time major champion has struggled to find success recently, missing the cut in four of his past six starts. Mickelson’s most recent top-10 finish at a major came three years ago, when he shot 17 under to place second at the British Open.

The 49-year-old looked visibly leaner in the video. Mickelson said he drank water and a “special coffee blend for wellness” created with Dave Phillips, a co-founder of the Titleist Performance Institute, during the six-day fast.

“I don’t know if it’s going to help me play better or not, but I’m willing to do whatever it takes to try to get my best back,” Mickelson said in the video.

USA Today/Golfweek reporter Steve DiMeglio confirmed Monday that the video was not Photoshopped after watching Mickelson during a practice session with Alex Noren and Matthew Baldwin.

“I didn’t fast to lose weight,” Mickelson told DiMeglio. “I fasted to heal.”

Mickelson has started doing yoga daily and hiking to improve his well-being, DiMeglio reported. He has now incorporated small amounts of food back into his plant-based diet after ending his fast late last week.

“Mechanically, my swing is right where I want it to be,” he said. "But mentally, I’ve just been losing focus. And my energy wasn’t there. So I needed to make changes.”

Mickelson will soon know whether the dietary changes benefit his performance, though he said he “does not have high expectations this week." The British Open begins Thursday at Royal Portrush Golf Club in Northern Ireland.

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