Once Alley decided to abandon her reckless lifestyle, she underwent drug rehabilitation and embraced Scientology, a religious belief created by the writer L. Ron Hubbard.
She struggled to get acting parts, first appearing on such television game shows as Match Game and Password Plus.
Her career breakthrough came when she landed her feature-film debut as Saavik, a Vulcan student, in Star Trek II: The Wrath of Khan (1982).
She followed the part with a major role in the television miniseries North and South. But it wasn't until she was selected to replace Shelly Long in the popular sitcom Cheers in the late 1980s that her rise to stardom began.
The combination of Alley's voluptuous beauty, throaty voice and comic timing earned her both a Golden Globe and an Emmy for her portrayal of the neurotic and high-strung Rebecca Howe in 1990.
During her years on Cheers, Alley's film career also took off. She showcased her dramatic talent in the 1988 thriller Shoot to Kill and had her first box-office hit with the comedy Look Who's Talking in 1989.
After Cheers bid farewell in 1993, Alley experienced some career highs and lows. She won an Emmy Award for the television movie David's Mother in 1994. Alley starred in the NBC sitcom Veronica's Closet in 1997, but the show received mixed reviews.
That same year, however, she was nominated for an Emmy Award for her supporting role on the dramatic miniseries The Last Don.
In 2005, the actress starred in Showtime's Fat Actress, an unscripted comedy about the media's obsession with celebrity weight. Alley also shared her personal experiences in her 2005 book How to Lose Your Ass and Regain Your Life.
Her publicized struggles with weight loss lead to Alley's affiliation with Jenny Craig weight loss centers. Appearing on Oprah Winfrey's talk show, she showed off her new figure by donning a bikini. Alley served as a Jenny Craig spokesperson until December 2007.
Alley signed a deal with Oprah Winfrey's Harpo Productions in March 2008 to develop television projects. During that year, however, she made more headlines for her changing shape than her professional efforts. Alley regained the weight she lost while on the Jenny Craig program.
She told People magazine in May 2009 that she "fell off the horse" and would have "to work harder than last time" to slim down. Alley hired a trainer to help her meet this goal, and she plans on releasing her own weight loss system in November.