"I have a hard time with portion control, so I have 1,200 calorie meals delivered," she tells Lucky's September issue. "But I also work out, so basically I'm starving. It sucks. I drink a lot of water."
Alba -- who welcomed daughter Honor with husband Cash Warren in 2008 -- adds that she's not gym-obsessed like so many of her Hollywood peers.
"In the gym, I have like five things to distract me: TV, iPod, magazines. Working partners are good, too, so you can chat and not just drown in your own misery," Alba says. "Sorry, does that sound bad? I just hate working out."
(Still, the Spy Kids 4 actress is quick to point out that "working out every day, even for just 45 minutes, is good for my mental state.")
Her fitness routine aside, Alba says she's looking forward to getting back in front of the camera. "I've kept my future in mind," she tells Lucky. "I wasn't going to be a flash in the pan. I want my career to last a long time."
"Why am I here?" she continues. "Sheer will and determination, dammit. . .and I hustled like crazy."