Inside Kate's Healthy New Look

On April 23, Kate Bosworth showed up at a Food Bank for New York City charity gala flaunting a noticeably fuller frame than she did last summer.

The 5-foot-5 actress, 24, had been "dangerously skinny at around 95 pounds, but she's gained 10 to 15 pounds since," estimates Beverly Hills nutritionist Jonny Bowden.

What was behind the weight gain?

"Kate stopped partying, started working out more, eating a bit more and generally doesn't care about her weight so much because she¹s happy," a source close to the actress says, noting that no dramatic intervention was staged.

Adds a longtime friend, "Stress can take its toll, and last fall was just hard for her." (Bosworth and Orlando Bloom, 30, split in September.) "Kate is human. We all go through tough times."

Now? The actress' new regimen includes strength-building activities like hiking.

"She's leading a happier, healthier lifestyle" with model beau James Rousseau, 26, says the pal.

Indeed, as Edward Abramson, author of Emotional Eating, tells Us, "Having a new relationship may have lifted her mood and restored her appetite."

Re: Inside Kate's Healthy New Look

Good for her! Her hair, skin, teeth, and menstrual cycle will thank her!