Born in Colorado Springs, he was the nephew of movie actor Lon Chaney. His family moved to San Francisco just before the devastating 1906 earthquake and fires. After the disaster, they moved across the bay to Berkeley, where he was identified as one of the 1,528 “gifted” children studied by Stanford University researcher Lewis Terman. Before Keys was out of his teens, he worked in a lumber camp, shoveled bat guano in an Arizona cave, mined for gold and sailed to China on an ocean liner as a member of the crew.

He graduated from the University of California at Berkeley and briefly took a management trainee job at Woolworth’s but soon was back in school, earning a doctorate in biology from the Scripps Institute in La Jolla, Calif. He had a postdoctoral fellowship in Copenhagen, earned a second doctorate in physiology from Kings College in Cambridge, England, and worked briefly at the Mayo Clinic. He joined the University of Minnesota in 1936 and four years later founded its famous Laboratory of Physiological Hygiene, housed under the bleachers at the university’s stadium.

He led a scientific excursion to the Andes in 1935 to study the physiological effects of altitude. It was that research, he believed, which led to an assignment from the U.S. government at the start of World War II: design a lightweight but nutritionally robust ration for paratroops. The K Ration, named for him, was originally made up of items from a Minneapolis grocery store — hard biscuits, dry sausage, hard candy and chocolate.

Dr. Keys, by then a special assistant to the secretary of war, did other nutrition research, and his study on the physiology of starvation, conducted in Minnesota on conscientious objectors, provided the most complete record of the physiological, psychological and cognitive changes that come from food deprivation.

In 1947, he noticed the increasing numbers of deaths from heart attacks, as noted in the newspapers’ obituary pages, and began to study 283 businessmen from the Twin Cities, conducting examinations and taking blood samples every five years. It showed that smoking, high blood pressure and elevated cholesterol were frequently seen in men who had heart attacks. After a decade of work, he determined that saturated fat chiefly determined blood cholesterol levels, a breakthrough that stunned the meat-and-potatoes populace.

That work led him to create the Seven Countries Study, which is still considered one of the most rigorous and complicated epidemiological studies ever undertaken.

The insights, popularized in his bestseller “Eat Well and Stay Well,” which he wrote with his wife, landed Dr. Keys on the cover of Time magazine in 1961. The profits from that book and two similar ones allowed the family to buy a home in Italy, where they lived when they weren’t in Minnesota. He retired in 1972 from the university. He remained physically active for decades, walking, swimming and building stone walls.

Survivors include his wife, Margaret Keys, of Minneapolis; a daughter, Carrie D’Andrea of Bloomington, Minn.; a son, Dr. Henry Keys of Voorheesville, N.Y.; eight grandchildren; and six great-grandchildren.

Ever the rigorous scientist, Dr. Keys was asked at his 100th birthday party in January whether his diet had contributed to his long life. He answered, “Very likely, but no proof.”