Coming off a left-knee injury that cost him the entire 2017 NFL season, Garnett had two crucial objectives: to get his knee healthy and to drastically change his body so he would have a better chance at success in coach Kyle Shanahan's offense.
Recovering from knee surgery was simply a matter of time and rehab. For Garnett, who at his heaviest was 326 pounds and 27 percent body fat, getting into shape was a more arduous task.
"The hardest part was really the mindset," Garnett said. "A lot of times, footballwise, I think I'm going to go as hard as I can on the field. But you have got to think about it like, 'Oh, when I'm at home, I'm still gonna go hard.' Things like not eating this after 8 o'clock and I'm going to drink the protein water instead. Or maybe if I want to eat those Skittles, this time I'm going to put that down and I'm not going to eat that this time. It's those mental battles."
Day by day and meal by meal, Garnett, a first-round pick by the 49ers in 2016, claimed enough small victories to return to the team's offseason program in the best shape of his short NFL career. Stories of players arriving at training camp or offseason programs talking about being in their best shape have become cliché, but for Garnett the journey could be career-defining as he enters his third season.
Garnett returned to the Niners at 304 pounds and reduced his body fat from 27 to 21 percent.
"He took care of his body in the time away," Shanahan said. "Where he is right now is much further ahead to where he was last year in OTAs when I met him. He's in better shape, he runs better, he's stronger, he's lighter and he is giving himself a chance to compete now.”
To reach that point, Garnett had to do more than just go on a crash diet. He had to change the way he looks at food. Instead of eating for pleasure, Garnett aimed to view every meal as a chance to fuel his body. That meant eliminating vices such as soda, candy and alcohol. If Garnett was hungry late at night, it meant resisting a trip to Taco Bell.
Garnett also didn't hesitate to lean on the Niners' coaching and support staff. Nutrition coordinator Jordan Mazur and director of functional performance Elliott Williams helped Garnett devise meal plans, while the strength and conditioning staff led by Ray Wright put together a workout plan that would complement both his rehab and his weight-loss efforts.
"The coaches asked me, 'Hey, we want you to be here and we want you to be this body fat and this weight,'" Garnett said. "It's like, 'Well, I'm a professional athlete, it's my onus. They are not going to hold my hand.'"
Garnett used to eat healthy meals from Monday to Thursday at the team facility -- only to return to a house with no food and end up eating unhealthily. Now his meals are meticulously planned. When Garnett would visit the team cafeteria during his rehab, he'd have breakfast, lunch and dinner already pre-packaged and waiting for him. Those meals included plenty of lean proteins like chicken or fish and vegetables.
On weekends, Garnett relies on a local delivery service called LoCal Foodz to provide him with healthy meal options and prevent temptation. Whenever Garnett would be tempted to stray, he'd think of how far removed he had become from the first-round pick who had the potential to be a long-term starter in the league.
"I really felt like this injury was the best thing for me to where I can come back a new player, new body, new physique and if I can learn and get the techniques back that I had and get the power I had back with all these things I know now, I can really be that player that I know I can be," Garnett said.
When Garnett returned to the practice field, there was an adjustment period. In the spring, he split reps with the starting offense at right guard, rotating with Mike Person. He had to learn to trust that his knee would hold up, but also how best to use his rebuilt frame.
With each spring practice, Garnett said he felt better about how his knee was responding. He might have been a half-step off on his timing sometimes, but he was encouraged by the fact that he was close after only a handful of practices.
"It's not a 'Hey, is my knee going to give out during practice and am I able to make it through?'" Garnett said. "That's aside, that question has been answered. The next question is can I compete and earn my spot back and earn my job and can I get the techniques down for whatever this team needs me to do?"
Along with the loss of weight, Garnett also became quicker and more explosive out of his stance. That change comes with a tweak to Garnett's technique, as he must now remind himself to stay lower, noting that his lower mass means he needs more acceleration in order to generate force through his blocks.
As the 49ers exited their offseason program, Garnett had no luxury vacations reserved. His summer plans involved continuing to eat right and spending plenty of time in the weight room. His goal? To cut a figure similar to that of Niners left tackle Joe Staley, who is a chiseled 295 pounds and one of the most athletic linemen in the league.
Alas, despite such a successful offseason, Garnett again finds himself in a tenuous position. The same left knee that kept him out of football last season has caused further problems in this training camp, costing him valuable practice repetitions and putting him behind the curve once again.
If Garnett can catch up and prove he's capable of getting to the second and third level in Shanahan's outside-zone scheme, Garnett will have a chance to nail down a roster spot and, potentially, compete for a starting job in 2018.
"I kind of reset my football brain and reset that football mindset to where I'm not a power football player anymore,” Garnett said. "I still have that crazy switch I can turn on if Coach calls power, but really focusing on the techniques that we're using here, really focusing on the outside zone. It is a completely different scheme. It's completely different footwork. So it's really about listening to the coaches and just erasing that mind and focusing on the new Josh."