DUNEDIN, Fla. -- No meat. No dairy. No excuses.

So went the six-word summary of Mike Fiers' Saturday at Dunedin Stadium.

First, the dietary news: As first revealed through dry-erase board scrawling in the Tigers' home clubhouse at Joker Marchant Stadium, Fiers is on a "vegan adventure." Fiers acknowledged that he's allowing some seafood -- "a little shrimp, here and there," he said -- but otherwise has avoided meat and dairy for the past seven days.

"I feel amazing," Fiers said after his three-inning start in the Tigers' 6-3 loss to the Blue Jays. "It's been a week, and I'm going to keep doing it. I feel great. I feel like I have more energy.

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"Everything feels better -- waking up, going to bed, feeling great throughout the day. Everyone said I might lose velocity, but I actually feel better. So I'm going to stick with it and see where it goes."

OK. Back to baseball, at least for a moment: Fiers surrendered five earned runs Saturday, all in a fretful first inning in which he walked three batters, uncorked a wild pitch, and generally struggled to locate his pitches.

Fiers was much better over the subsequent two innings. And he's assured of a rotation spot after signing a one-year, $6 million contract. "He's a veteran," Tigers manager Ron Gardenhire said. "The ball's coming out of his hand. He's healthy. That's all we're looking for."

But Fiers wasn't about to dismiss the results.

"I've still got to prove [something] to these guys," Fiers said. "Whatever you did in the past, it's a new year, and I've got to pitch better than this -- even in spring. You can say you're working on stuff, but I think that's just an excuse for not pitching well. I'm not going to say that. It's me not getting ahead, [instead of] throwing more strikes early and expanding late."

Fiers said he's "100 percent" healthy and was not bothered by any back or arm issues during Saturday's start.

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"I don't want to be the bullpen warrior, where you're lights-out in the bullpen, you come into the game, and you don't look like you know what you're doing," Fiers said. "Those guys don't pitch in the big leagues. I've got to get away from that. I need to be able to pitch how I pitch in the bullpen: attack the hitters, get ahead, put them away late."

As for the dietary change, Fiers cited a simple reason.

"Health," he said. "I'm 32. Just your body feeling good and being able to have more stamina, be out there pitching. ... I've been trying it out. I've always wanted to try something. Some things work. Some things don't. Right now, I'm a week in. I feel great, so I'm going to keep it up."

And his vegan mentor is a former Tiger.

"Last year, Cameron Maybin came over to Houston, and he was big on it," Fiers said. "He watched the movie 'What the Health.' He was telling us a couple things from it. I watched it a week ago, and I stopped eating meat and dairy a week ago. There's a lot of information out there that tells that it's bad for you. Yeah, it's one-sided, that movie. But a lot of things made sense to me, and I'm going to try it."

For now, that has meant more fruits and vegetables -- especially those with protein. He's eating a lot of beans and rice. And he's being teased by "everybody" in the clubhouse, by his estimation.

" Shane Greene tried it last year, I think," Fiers said. "A couple guys have tried it. Those guys are behind me and pushed me to do it. They're telling me to 'stay strong,' jokingly. I love it. I'm going to keep doing it."

Jon Paul Morosi is a reporter for MLB.com and covered the Tigers on Saturday.