Jessica Alba looks like she's enjoying her Thailand vacation, but the actress has some of her fans back in the States worried over a recent bikini pic she posted to her Instagram account.

In the snapshot, the brunette beauty and a friend "jump for joy" in front of a picturesque background, but it's Jessica's skinny body, not the scenery, that has people talking.

The 33-year-old has always been in good shape, often taking roles that don't require a whole lot of clothing (see 'Sin City,' 'Honey' and countless others). But a few of her followers expressed concern over "seeing her ribs" in the photo above.

Jessica opened up about her diet this past summer, stating that she pretty much follows the same regimen as her two young daughters, Honor, 6, and Haven, 3.

“I have the same food philosophy for myself as I do for my kids," she told 'Self' magazine. "We eat mostly lean protein and fresh fruit and vegetables, nothing processed or from a box, if we can. For me, when I don’t eat a ton of carbs, I have more energy.”

But, like the rest of us, the 'Fantastic Four' star doesn't always follow the rules!

“I’ll for sure have a piece of chocolate," she told the mag. "I will mow through a bowl of guacamole. If I’m not going to have dessert, I’ll have a martini.”

It's your turn to weigh in: Do you think Jessica's too skinny? Sound off in the comments section.