"I'm running around after a 3½-year-old so that always keeps you on your toes," the actress, 30, told reporters at an In Style/Forevermark event Tuesday at the Beverly Hills Hotel.
Along with chasing after daughter Honor, Alba also credits keeping a tighter rein on her cravings while expecting baby Haven, born in August.
"It was my second pregnancy so I think I just didn't indulge as much," she explains. "It was easier to snap back."
Working out with her friend Kelly Patricof has also proven effective for Alba – although she admits, "we complain a lot." Their least favorite move? "Burpees" – and they're not what you think.
The exercise "hurts your feelings," the Honest Company co-founder jokes. "You have to squat down, do a push up and then clap your hands above your head."
“We have a very mean trainer,” Patricof adds.
While expectant celebrity pals like Jessica Simpson have publicly declared their desire to have her post-pregnancy body, working on her fitness isn't a high priority for Alba at home.
"I just feel thankful and blessed that I have two beautiful children," she says. "That's my focus."