How skinny is too skinny?

Hollywood stars love looking lean, but sometimes they take their desire to be skinny to dangerous lengths.

From the hottest reality stars and super models to big screen bombshells, RadarOnline.com has photos of 10 stars who have gone too far with their dieting and ended up with scary skinny status.

Bethenny Frankel’s skeletal figure has sparked concern among fans over recent months, and the Bethenny Ever After star looked more emaciated than ever when she walked the streets of Manhattan on Sunday, and RadarOnline.com can exclusively reveal that her dramatic weight loss could have serious health risks.

“While she has always been thin, I think the stress of her new found success, the battles that have come because of that, the gut renovation of her apartment and the troubles in her marriage have probably led her to eat less due to the stress,” nutritional expert Dr. Fred Pescatore, who has not treated the reality star, told RadarOnline.com in an exclusive interview.

Nicole Richie struggled with an eating disorder in her younger years, but the Fashion Star judge has finally learned to embrace her body!

In a new interview with Glamour magazine, the 30-year-old opens up about her body image issues and reveals how she has changed her outlook since her ‘scary skinny’ scandal.

Too skinny is not sexy!

Hollywood’s hottest stars are famous for dieting and exercising their way too hot bodies, but sometimes they take their skinny obsession too far -- resulting in a scary skinny look that is anything but sexy! RadarOnline.com has photos of 10 stars who have showed off their bones in bikinis.

Nicole Richie struggled with her weight in her younger years, until she started to drop pounds post Simple Life. But Paris Hilton’s former sidekick took her weight loss fixation too far, culminating in a scary skin and bones bikini body that was captured on camera as she jogged on the beaches of Malibu.

Ali and Lindsay Lohan had their version of lunch on Friday, each having a cup of coffee at La Conversation Cafe in West Hollywood.

The girls certainly had much to talk about. As RadarOnline.com has been reporting, Lindsay is being investigated for allegedly assaulting a woman in the nightclub at the Standard Hotel earlier this month. She also reportedly got into a drink-throwing incident at the same night spot on Wednesday.

Hey, get a room!

Jason Statham and Rosie Huntington-Whiteley aren't the least bit shy about love affair.

The gorgeous pair cuddled, kissed  and hugged each other poolside in Miami, and RadarOnline.com has the pictures.

PHOTOS  Jason Statham And Rosie Huntington-Whiteley Get Their PDA On In Miami

The Transporter star, 44, and the model-turned actress, 24, have been together two years, but it never seems to get old for the pair.

As RadarOnline.com previously reported, a top nutritionist says Huntington-Whiteley is looking too skinny these days.

Dr. Majid Ali told us the 5'9" Brit looks to be weighing only about 100 lbs.

Boyfriend Jason doesn't seem to mind.

Ali Lohan showed off her pencil-thin figure in Hawaii Friday.

The 17-year-old model is on the island of Oahu with big sis Lindsay, and was spotted in super-short cut-off jeans and a midriff-baring tank top.

As RadarOnline.com previously reported, Lindsay was invited to attend the Pipeline Masters surfing competition where her friend Any Irons was being honored. Irons was a legendary pro surfer who died of a drug overdose last year.

After watching some of the competition, the Lohan girls walked to a nearby convenience store for refreshments, but not before Ali playfully sent a karate-like kick in the direction of a friend.

PHOTOS: Scary Skinny Ali Lohan Visits Hawaii With Lindsay

Earlier in the week, Ali attended a casting call in Beverly Hills where Us magazine described her as "alarmingly gaunt and pale -- with noticeably stick-thin arms and legs."

Ali, who towers over Lindsay, turns 18 December 22. She so far hasn't commented on Lindsay's Playboy pictorial which was leaked on the Internet on Friday.

PHOTOS: Lindsay Lohan Surfs Away From Playboy Controversy In Hawaii

Lindsay Lohan’s little sister Ali, is a brunette beauty with a blossoming modeling career but in these shocking new photos obtained by RadarOnline.com the teenager’s gaunt face is causing alarm in her family.

Ali, 17, was snapped in Beverly Hills on Tuesday and her thin frame is a stark contrast to the healthy looking girl she was just five months ago, when photographed in March.

PHOTOS: Ali Lohan Is Looking Scary Skinny