Fitness guru Richard Simmons dead at 76

Eccentric fitness guru Richard Simmons, known for his unrelenting positivity, has died, according to his representative.

Simmons just celebrated his 76th birthday on Friday.

The Los Angeles Police Department responded to his home after a 911 call from his housekeeper and found Simmons dead, according to police sources. He appears to have died of natural causes, and no foul play is suspected, the sources said.

Simmons had spooked fans just three months ago when he posted that he was dying on Facebook, writing in March, "I have some news to tell you. Please don't be sad. I am .... dying. Oh I can see your faces now. The truth is we all are dying. Every day we live we are getting closer to our death."

He later clarified that he was not actually dying, but that the message was intended to encourage everyone to "embrace every day that we have."

Simmons has been out of the public eye lately, though there were reports of a biopic being made about the fitness enthusiast earlier this year. Simmons criticized the reports, writing, "Don't believe everything you read. I no longer have a manager, and I no longer have a publicist. I just try to live a quiet life and be peaceful."

Simmons posted prolifically on social media, often several times a day. He posted about his birthday on Facebook a day before his death, writing, "Thank you...I never got so many messages about my birthday in my life! I am sitting here writing emails. Have a most beautiful rest of your Friday."

He told his fans in March that he'd had skin cancer removed from his face, but was now doing well.

"I know some of you reading this have had cancer or have known someone in your life who has had cancer," he wrote. "Promise me you will see your doctor and get a complete check up."

He was born Milton Teagle Simmons in New Orleans on July 12, 1948, but adopted the name Richard while growing up.

Simmons has often talked about how he was overweight as a child, which led him to his weight loss journey and pursuit of a career in fitness starting in the 1970s and '80s. His first foray into weight loss came with the opening of his gym, Slimmons, in Beverly Hills, California.

He released his first book, "Never Say Diet," in 1980. The book was the first of 12 he would release in his career.

His line of fitness videos exploded in popularity in the 1980s, along with a nationwide fitness craze that included a growing popularity of aerobics and Jazzercise. His videos, including the "Sweatin' to the Oldies" series, became some of the most popular videos of the era.

Simmons also made regular TV appearances, including as a regular on talk shows from the "Late Show with David Letterman" to the "Rosie O'Donnell Show." He also had a regular role on the soap opera "General Hospital" and made guest appearances as himself on shows such as "Arrested Development" and "The Larry Sanders Show."

He also hosted his own talk and fitness show, "The Richard Simmons Show," from 1980 to 1984. The show won four Daytime Emmy Awards.

ABC News' Bonnie McLean contributed to this report.