Sources close to the ‘Mean Girls’ star say that hard-partying Lindsay is surviving off Red Bull, coffee and cigarettes; is hardly sleeping; and making strange phone-calls at odd hours of the night.

All that combined with the stress of her rocky relationship with Ronson is clearly taking its toll in a dangerous way.

"Now Sam and Lindsay are being marketed as the D.J./hosting couple and are earning good money off it, but that means Lindsay is going out more and more and hanging around a bad crowd," ‘Fox News’ quoted an insider as saying.

The source added: "It doesn’t take brain surgery to figure out how’s she lost weight so fast …"

According to Fred DeVito, Nutrition/Fitness Expert and Founder of Exhale Spa’s Core Fusion: "Looking at photos of Lindsay just over last month, there is obviously not only an obvious loss of weight but also a loss of muscle mass. A lack of muscle could lead to rapid weight gains in the long-term and a vicious cycle of yo-yo dieting.”

However, in an interview with ‘Us’ magazine, the actress said that there were no problems in her romance with Ronson, and the weight loss was due to her hectic life and totally unintentional.

However, the source said: "Lindsay is in a really bad place and refuses to believe anything is wrong.”