At 30 years old, Brooks says his metabolism has slowed down, and admitted his extra pounds could be affecting his performance "maybe a little bit," according to the San Francisco Chronicle.
Defensive coordinator Vic Fangio is more certain.
"He's gotten a few extra pounds on him now that I think is holding him back," Fangio said. "We've been trying hard to get that off of him, and hopefully he'll be back to the guy that we saw, really that we've seen for three years."
Brooks made the Pro Bowl in 2013 and was named a second team All-Pro in both of the last two seasons.
The linebacker said he wants to lose between five and 10 pounds, but knows it likely won't happen before the season opener on Sept. 7.
"It takes time. You just can't do all that in a week, or two weeks," he said.
- Molly Geary