I heard it's not the zone diet that she's on but that she had turned vegan and followed the same lifestyle that Alanis Morisette is following.

Sandra is NOT a vegetarian: "Her trainer, Eden Paul, based in Los Angeles, has worked with her to get her in shape for the film. It was not an easy routine, Paul admits, but Bullock did it without complaining because she really wanted to be convincing for the part. “She wanted to emulate her character and look buff and smashing in suits. We love to incorporate plyometrics, weights, Pilates and boxing.” Paul explains. Bullock adds she gets her motivation from knowing that it’s part of her job to look this good – “People ask, ‘How do actresses do it?’ Um, they pay us to do this in order to look good on film.” As for diet, Sandra is the adept of the “weekly cheat day” rule, meaning, she allows herself one day a week when she can eat whatever she wants. This helps her stay motivated for the rest of the time, and concentrate on eating healthy. Speaking of which, Bullock admits she does not diet, choosing instead to avoid junk food and fatty foods in general and eating only stuff that she knows is good for her, such as fish, chicken and lots of vegetables. “Last night I had brown rice and black beans and some steamed vegetables so today I’m going to have all kinds of good stuff! I love sweets, like Viennese pastry, raw cookie dough, or a nice bowl of Lucky Charms with milk that I eat in bed watching SNL. That’s heaven right there. I really changed my eating habits, from pizza and Diet Coke to something like maybe a piece of chicken and some vegetables on the side.” the actress reveals in the same interview. " http://news.softpedia.com/news/Sandra-Bullock-s-Diet-and-Workout-to-Look-Fab-at-45-116133.shtml