"Courtney's weight issue -- which he does need some pounds -- is that he doesn't eat right," Harbaugh told the club's website. "Courtney eats too much and he doesn't eat all the right foods.
"He knows that and that's something he's going to have to get a handle on, or he's not going to be the best he can be. But he's aware of it. Everybody in our building is involved with it. He'll be in fighting shape, I promise you that."
Upshaw, who is up to 285 pounds after being listed at 272 last season, apparently knows he has an issue. He skipped the club's visit to the White House earlier this week to work out and meet with a nutritionist, according to the team's website.
"I'm working, man. I'm working real hard," Upshaw said Thursday. "It's anything to try to get me down. It's frustrating to not see my weight go down knowing I'm putting in all that work."
As a rookie, Upshaw encountered similar issues. However, he worked the pounds off, started nine of 16 games and had 60 tackles and 1½ sacks for the Super Bowl champions.
"It's frustrating because I had to go through the same thing last year. But I did it," Upshaw said.
"This offseason I didn't really train the way I should have because of those personal situations I had to deal with back in Alabama. So when I was in Baltimore I was training, but when I was in Alabama I didn't really do too much. But I'm working every day."