Rick Hersh told the AP that LaLanne died of respiratory failure from pneumonia Sunday at his home in Morro Bay, Calif.
LaLanne ate healthy and exercised every day of his life up until the end, Hersh said.
"He never lost enthusiasm for life and physical fitness," Bob Barker, the 87-year-old former Price is Right host, told the AP. "I saw him in about 2007 and he still looked remarkably good. He still looked like the same enthusiastic guy that he always was."
LaLanne's show was on television from the 1950s into the '80s. He kept things simple and upbeat on his programs, telling children to drag their mothers in front of the TV set and demonstrating exercises that used just a chair or a towel instead of fancy, expensive equipment.
He also founded a chain of namesake fitness studios and in recent years marketed Jack LaLanne's Power Juicer in infomercials. He maintained a youthful physique and used to joke: "I can't afford to die. It would wreck my image."
He made various appearances on CNN's Larry King Live. "There was no one like Jack LaLanne," Larry King, 87, said Sunday night. "He would go on forever ... a true guru. I guess Charles Atlas from the old comic books would be the predecessor for Jack LaLanne."
Arnold Schwarzenegger once credited LaLanne with taking exercise out of the gym and into living rooms.
LaLanne said his own daily routine usually consisted of two hours of weightlifting and an hour in the swimming pool. "It's a lifestyle, it's something you do the rest of your life," LaLanne said. "How long are you going to keep breathing? How long do you keep eating? You just do it."
Elaine LaLanne, his wife of 51 years who frequently appeared with him on television, said: "I have not only lost my husband and a great American icon, but the best friend and most loving partner anyone could ever hope for."
Besides his wife, he is survived by two sons, Dan and Jon, and a daughter, Yvonne.