Wikipedia takes a skeptic's view of Walker and says he died at 99. There's some evidence that's correct. It's also consistent with this 1933 New York Times account of a Norman Walker who ran a Brooklyn Institute of Ortho-Dietetics and was found guilty of bilking the institute's students out of $150 in tuition. That Norman Walker was 46 at the time; he would have been 99 in 1985.
Walker himself was circumspect about his age. In 1972, he wrote: "How old am I? I am ageless."
He was, however, forthcoming about the cause of his longevity (however long it was). For most of his life, Walker sold juice and the promise that a diet of raw foods—particularly in liquid form—were a source of health and wellness.
One of the founders of today's juice movement, Walker was born in Europe but immigrated to the United States as a young man. He eventually made his way to California, where he opened a juice bar, and then to the southwest, where he churned out a series of health books. At some point, he started calling himself Dr. Norman W. Walker, although it's unclear when he earned the Ph.D. he said he had.
The origin story of his juice revelation is set in France, where he had gone to convalesce after a breakdown. He watched, the story goes, one of his hosts peel carrots and noticed how wet the insides of the peels were. He borrowed a feed grinder and ran some carrots through it—he had created carrot juice.
By the time he had reached California, he was searching for a better method for creating the juice he was selling. The manual juicers that existed at the time, he thought, could not extract all the value from the raw fruits and vegetables he was juicing. He wrote in one of his books:
No practical hand juicer has been found by us that can possibly extract all of the vital elements from the vegetables, as they only partly crush the fibers but do not triturate them [grind them finely], and trituration is the fundamenal [sic] principle, discovered by the Norwalk Laboratory of Nutritional Chemistry and Scientific Research, in the liberation and reclamation of these vital elements.
So he created a mechanical juicer that ground vegetables into teeny-tiny pieces. (The juice still had to be pressed by hand.) The descendant of that juicer, the Norwalk 280, is still considered one of the best juicers on the market today—it's priced at $2,495. Or you could save some money and just eat the vegetables whole.