Guerrero, 21, recently said he was up to 280 pounds when training camp resumed in July after the COVID-19 shutdown. The former top prospect added that he's already dropped 12 pounds since the season ended.
"I did not get to the second training well, and I told myself that this cannot happen again. I was overweight, I said that it couldn't happen again, and I got to work at once," Guerrero told Yancen Pujols of El Caribe, as translated via Google Translate.
Guerrero said he apologized to his teammates for being out of shape during the season and admitted he needed to work harder to reach his full potential going forward.
"Things happen because you don't work. ... I learned after these months of the coronavirus that if you don't work hard you can't be in the major leagues. Why do (Fernando) Tatis (Jr.) and (Juan) Soto put good numbers? Because they work hard," he said. "I hit the hits I hit because of the ability that God gave me. But I knew it from the beginning. I know I did it wrong.
"I apologized to my teammates and decided to play like this, but I did it wrong."
In addition to training, Guerrero said he's changed his diet to reduce his fat intake and eats dinner every night at the same time. He added that his ideal weight is 240-245 pounds.
Vladito has been chronicling his progress on Instagram since mid-October:
After he played exclusively at third base in the minors and for Toronto in 2019, the Blue Jays moved Guerrero to first in 2020. At the plate, he hit .262/.329/.462 with nine home runs while appearing in all 60 games this summer.