"Brians vision and personal insight into the nutritional needs of athletes helped to launch the energy bar category," said a statement from PowerBar Inc.
"Brian will be remembered as a dynamic innovator, whose passion was to help athletes perform at their best. Brians generosity and commitment to others was deeply felt by those around him."
Since the purchase of PowerBar by Nestle S.A. in 2000 for $375m, Maxwell had served on various charitable, educational and arts boards.
According to the Canadian Press Association, Maxwell collapsed at a post office in San Anselmo, California, and paramedics were unable to revive him. He died at a local hospital.