Rose E. Frisch, a scientist whose influential work showed that women without enough body fat would have trouble becoming pregnant, but that they also had a lower risk of breast cancer, died on Jan. 30 at an assisted-living facility in Cambridge, Mass. She was 96.
Her death was confirmed by her son, Henry.
Dr. Frisch, who spent decades at the Harvard Center for Population and Development Studies, conducted research that helped lay the theoretical groundwork for the discovery of the hormone leptin, which is important in regulating appetite, fat and puberty.
Starting with a 1974 study that she researched and published with a colleague, her work found that girls with little fat, especially serious athletes or those with eating disorders like anorexia, would begin menstruating later and experience delayed or interrupted fertility. Once they acquired at least 17 percent body fat, she estimated, they would experience no apparent difficulty becoming pregnant.
Some athletes even named their daughters Rose because they became pregnant after reducing their exercise regimens and gaining sufficient weight, Henry Frisch said. He added that women, especially runners, would contact his mother to ask how much weight they should gain to have children.
Dr. Frisch, in a 1985 study, also found that athletes were less likely to develop breast cancer, apparently because of reduced estrogen exposure.
Her career path was strewn with obstacles. Female scientists were scarce at Harvard when she started there, and she was in her 40s, having stayed home until her two children had finished elementary school.
“Not only was it hard to be a woman in that role, but the subject matter she was talking about, sex and menarche and fertility, were things not many people discussed,” said Lisa Berkman, the director of the population center at Harvard. “The men at the Pop Center would ask her to take notes as if she were a secretary, and there she was, equally strong as a scientist.”
Dr. Frisch complied and complained, Dr. Berkman said, but she “certainly didn’t back off from wanting to be at the table.”
Henry Frisch, a physicist, said his mother had also benefited from that environment. Not expecting to receive tenure or equal treatment, she and other women were “free to follow paths that weren’t conventional,” he said.
Still, he said, she was paid so little that the National Institutes of Health once called to say a grant application she had submitted should list her annual salary, not her monthly salary. “That is my annual salary,” she replied.
She was born Rose Epstein on July 7, 1918, in the Bronx, to Louis and Stella Epstein. She was captivated by the 1926 book “Microbe Hunters,” by Paul de Kruif, which described the pioneering discoveries of Leeuwenhoek, Pasteur and other scientists.
She was encouraged to attend Smith College by her brother, Lee Eastman, a lawyer who had changed his surname and whose daughter Linda would marry Paul McCartney.
Rose’s education was partly financed by the Leopold Schepp Foundation, established to help young people develop good character.
At Smith, she met a Princeton physics student, David Frisch, on a blind date. That night, she wrote in her diary, “I just met the man I am going to marry.” They attended graduate school at the University of Wisconsin-Madison; Rose studied the genetics of fruit flies. Then, as World War II erupted, David was sent to the fledgling Manhattan Project at Los Alamos, N.M.
There, Henry Frisch said, Rose worked for the physicist Richard Feynman, serving as a “computer,” typing numbers into a mechanical machine and “solving equations, crunching numbers.”
In 1945, after nuclear bombs were dropped on Hiroshima and Nagasaki, the Frisches, disillusioned by the damage done, left Los Alamos for Cambridge, where David joined the Massachusetts Institute of Technology and Rose raised Henry and a daughter, Ruth Frisch Dealy, an artist. Both children survive her, as do four grandchildren and three great-grandchildren. David Frisch died in 1991.
Dr. Frisch’s idea to link body fat to fertility drew from a history of observations in animals, “pigeons all the way up to elephants,” her son said.
“If you feed cattle well, the twinning rate goes up,” Henry Frisch said. “She was very much at home with animal breeders.”
Her research focused on ballet dancers and athletes like swimmers and rowers. She had several research collaborators, including, on some studies, Dr. Tenley Albright, the first American Olympic gold medalist in women’s figure skating and a surgeon specializing in women’s disorders.
Dr. Frisch was a fellow of the American Academy of Arts and Sciences and the author of a book for general audiences, “Female Fertility and the Body Fat Connection,” as well as a children’s book about nutrition, “Plants That Feed the World.”
Henry Frisch said his mother was “very single-minded about her science.”
Once, he said, he found his parents “basically not speaking to each other” after debating “if a lightning bolt hits a big bowl of amino acids, can you make a baby?” — a version of a well-known scientific question about how life can form.
“My dad says, ‘Yes, if you have the right molecules, you can put them together to make a baby,’ ” Henry Frisch said. “My mother said this was not only nonsense, but unbelievable nonsense. After all those years of marriage, they had run onto a fundamental rock.”
Dr. Berkman said Dr. Frisch was equally strong-willed in advocating her research; until several years ago, although physically frail, she came to her Harvard office and wrote letters to scientific journals, “trying to link new findings to her work, to point out the continued importance,” so that doctors would apply the science to treating women appropriately.
She was reminded of that importance in ways that sometimes said as much about men as her work did about women. At one conference, her son said, she was challenged by a respected scientist about her research on fat and fertility. But after her talk, the scientist came to the lectern. How much weight, he wanted to know, should his anorexic daughter gain so she could become pregnant?