Jack LaLanne: Nutritionist and fitness guru celebrated for his spectacular stunts

"I can't die, it would ruin my image," was one of Jack LaLanne's catchphrases.

Long before Jane Fonda first felt the burn, or Robert Atkins created his diet, LaLanne (pronouced luh-LANE) was leading exercise and promoting healthy eating on television screens across America. Dressed in a tight-fitting black body-suit, using little more than a chair and a rubber stretching cord and accompanied by ice-rink organ music and an Alsatian dog named Happy, he led exercises while maintaining a steady fevre-pitched stream of patter, half evangelist and half pitchman, always good natured and punctuated exclusively with exclamation marks! He became known as the "father of American fitness", something he could have hardly foreseen when he started his first gym in Oakland in 1936. "Back then I was a crackpot," LaLanne joked in 1995. "Today I'm an authority."

LaLanne's style owed much to Paul Bragg, a proselytising nutritionist whom his mother took him to see when he was 15. Francois Henri LaLanne was born in San Francisco 26 September 1914, to French immigrant parents, and given the nickname Jack by his brother. Some of his talent may have been inherited; his father was a part-time dance instructor and his mother a fervent Seventh-Day Adventist. The family moved to Bakersfield, where his father's attempt at sheep-farming failed; his father died of a heart attack aged 50. Growing up in Oakland, his mother spoiled him with sweets; the adolescent LaLanne was skinny, pimply, myopic; the classic seven-stone weakling. This changed after she took him to see Bragg at a public lecture. Brought to the stage as they looked for seats, Bragg called him "a walking garbage can" and offered, as LaLanne phrased it, "salvation". In other accounts he called it an exorcism. He never ate another sweet.

Exercise and diet turned him into an athlete, and after high school he began training prospective police and firemen to pass the fitness exams. Vic Tanny may have opened his own gym earlier, in Cleveland, but LaLanne's was a fitness centre before the term was coined, including a health food store and juice bar. He attracted members by going to local high schools and getting the least fit students to volunteer for free treatment. His success with them generated word of mouth throughout the area, and soon he had a local chain of studios.

In 1951 he debuted on KGO, San Francisco's local ABC station, where he met his second wife, Elaine, who was a booker. Originally broadcast in the early morning, he told kids that "Uncle Jack" wanted them to get their parents up and make them exercise. His profile increased steadily, helped by stunts he undertook to attract attention. To prove 40 wasn't too old, he swam the length of the Golden Gate Bridge underwater, carrying two huge air tanks. In 1957 he swam the Golden Gate channel towing a 2,500lb cabin cruiser through the strong currents. And he set a world record by doing 1,033 push-ups in 23 minutes on the network TV show You Asked For It.

ABC took LaLanne's show national in 1959; it ran for another 25 years. He celebrated the event by doing 1,000 chin-ups and 1,000 star jumps in less than an hour and a half. His birthday stunts marked the passing decades. When he turned 60 he towed a mere 1,000lb boat from Alcatraz Island to Fisherman's Wharf, handcuffed and shackled to make it interesting. At 70, again handcuffed and shackled, he towed 70 rowing boats, plus passengers, across Long Beach harbour to the Queen Mary. Although he promised more for later birthdays, he admitted at 90 that Elaine forced him to attempt nothing more strenuous than towing her across the bathtub.

LaLanne's fitness routine included two two-hour work-outs, exercise and swimming against resistance, daily. He ate twice a day, mostly eggs, fish, and raw vegetables processed through one of the "Power Juicers" he sold through his shows. "If it tastes good, spit it out," formed the core of his nutritionial advice.

In 1963 President Kennedy appointed LaLanne to his inaugural commission on Physical Fitness, and he received the commission's Lifetime Award in 2007. He was admitted to the California Hall of Fame by Governor Arnold Schwarzenegger, who had once turned down LaLanne's challenge to match him at push-ups at Venice's Muscle Beach.

He also received the Spirit of Muscle Beach award, and, in 2002 his own star on Hollywood Boulevard. He guested on television shows as varied as Peter Gunn and The Simpsons, and memorably gave Uncle Fester fitness lessons on The Addams Family. In 1995 he published a biography, Live Young Forever, and his programme was revived by repeats on ESPN Classic Sports network. A radio show, Jack LaLanne Live! debuted on the internet in 2007.

Francois Henri LaLanne, nutritionist and fitness expert: born San Francisco 26 September 1914; married twice (one son, one daughter, one stepson); died Morro Bay, California 23 January 2011.