Jack LaLanne, whose obsession with grueling workouts and good nutrition, complemented by a salesman’s gift, brought him recognition as the founder of the modern fitness movement, died Sunday afternoon at his home in Morro Bay, Calif. He was 96.

The cause was respiratory failure resulting from pneumonia, said his son Dan Doyle.

A self-described emotional and physical wreck while growing up in the San Francisco area, Mr. LaLanne began turning his life around, as he often told it, after hearing a talk on proper diet when he was 15.

He started working out with weights when they were an oddity, and in 1936 he opened the prototype for the fitness spas to come — a gym, juice bar and health food store — in an old office building in Oakland.........