Mariota told reporters Monday that he added 5-to-10 pounds for health reasons.
"When it comes down to it, just being able to absorb the hits, being able to be healthy for a full year," Mariota told reporters.
"Those things haven't really happened yet, so I'm doing my best to be able to be on the front end of it and allow myself the opportunity to play all 16 [games]."
"I think when it comes down to it, just being able to absorb the hits, being able to be healthy for a full year," Mariota said. "Those things haven't really happened yet, so I'm doing my best to be able to be on the front end of it and allow myself the opportunity to play all 16 [games]."
Mariota has yet to play a full 16-game regular season during his NFL career. The four-year veteran started 12 games during his 2015 campaign. He started 15 games during the 2016 and 2017 seasons. Mariota started 13 games in 2018, while appearing in 14 games.
He missed one game last season with a pinched nerve and the first half of another game with a neck stinger. Mariota also missed the Titans' season finale due to an elbow issue. The No. 2 overall pick in the 2015 NFL Draft completed a career-best 68.9 percent of his throws for 2,528 yards, 11 touchdowns and eight interceptions in 2018.
"I think that's why we're trying to find a happy medium," Mariota said. "There isn't a specific number. It's really coming down to when I get out here, do I feel like I can move? Do I feel good with the weight? And if that is, just kind of continue to see how heavy I can get where I feel good and the happy medium is met."
He said he used a balance of dieting and exercise in order to put on "good weight" so that he wasn't sluggish. Mariota trained in Hawaii.
"I would say that Marcus looks good," Titans coach Mike Vrabel said. "[We're] looking for a strong player -- this is a big league. I can remember playing against John Elway and Dan Marino, and these quarterbacks that -- they're big men. We play against Deshaun [Watson], he's a big player, and Andrew Luck, so I just want to make sure that we're doing everything we can and he's doing everything he can to stay healthy and stay durable, and to be able to help us on the field."
Mariota is on the final year of his contract, earning a $20.9 million salary in 2019. He is listed at 6-foot-4, 222 pounds. The Titans also traded for former Miami Dolphins quarterback Ryan Tannehill this off-season.