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.

It’s hard to believe that Crystal Renn was ever a plus-sized model!

The 25-year-old catwalk crawler, who was formally a role model in the plus-sized model community, can’t stop losing weight! Hitting the 9th Annual Spring Dinner Dance New Year’s In April: A Fool’s Fete in New York City on Tuesday night, the newly blonde flaunted her even slimmer figure in a Zac Posen gown...

When Kirsten Haglund was crowned Miss America in 2008, she was a vision of health and happiness, making it hard to believe that the blonde beauty had suffered from severe anorexia-nervosa most of her life.

The Michigan beauty queen, 23, recently opened up to CNN about the shocking details of her illness, which began when she was only 12-years-old, and RadarOnline.com has the details.

It’s no secret that Christina Ricci struggled with an eating disorder as a teenager, but the Pan Am actress reveals new details about how being outed at 14 years old actually changed her life for the better. 

“Somebody actually found out about it and outed me while I was recovering,” the former child star reveals about her eating disorder in the April 2012 Marie Claire UK. “It was a horrifying thing to do to a 14-year-old trying to cope with a devastating illness.”

Demi Moore is well on the road to recovery!

The 49-year-old actress returned to Los Angeles on Saturday after a stint in rehab and a relaxing vacation in the Caribbean with friends and RadarOnline.com has exclusively learned that she is getting ready to head back to work.

Demi Moore sought professional treatment following her frightening collapse, seizure and hospitalization last month, and RadarOnline.com has exclusively learned that she is “doing well” in rehab.

The 49-year-old Ghost star has struggled in the last year with substance abuse issues and an eating disorder. She continued to spiral downward after splitting with her husband, Ashton Kutcher, last November after he was caught cheating on what would have been their sixth wedding anniversary.

When Demi Moore checked into the Cirque Lodge rehab treatment center in Utah for anorexia and an addiction to prescription pills, she wasn't allowed to see her weight on the scale, and was weighed backwards because her treatment team doesn't want her focused on how much she weighs, RadarOnline.com is exclusively reporting.

Demi hit rock bottom after her marriage to Ashton Kutcher ended when he was caught cheating on their sixth wedding anniversary with San Diego party girl Sara Leal.

Demi Moore's estranged husband Ashton Kutcher was photographed going to her Benedict Canyon estate on Wednesday, but that wasn't his first visit to her since her hospitalization, and RadarOnline.com has exclusively learned that the Two and a Half Men star has been praying with Demi, and offering support during this tumultuous time in her life.

As RadarOnline.com previously reported, the 49-year-old actress has been struggling with anorexia and had been taking the prescription drug Adderall leading up to her seizure on January 23.

Despite having a seizure, collapsing and being rushed to the hospital Demi Moore is in denial about her problems RadarOnline.com has exclusively learned.

The 49-year-old actress has been struggling with anorexia and taking the prescription pills Adderall leading up to her seizure on January 23. 

However, despite pressure from those around her to seek help for her problems, and the statement that her rep released saying she was doing so, Demi is pushing back at friends.

Rumer Willis is trying to maintain a sense of normalcy after her mother's scary ordeal last week.

The 23-year-old aspiring actress was spotted running errands on Monday just one week after a frantic 9-1-1 call was made from her mom Demi Moore's home saying that she had "smoked something" and was "having convulsions."

PHOTOS: Rumer Willis Runs Errands In L.A.

Demi, 49, was rushed to the hospital and is going to seek treatment for her anorexia among other issues, but she has not been spotted since her hospital stay.