The first point Dr. Franz Halberg wants to make about his little-known science of chronobiology is that it is not biorhythm.

Biorhythm, a faddish pseudoscience, is based on a single variable, birth date, and involves three fixed cycles for physical, emotional and mental highs and lows.

"No serious scientist has ever supposed for a moment that there was any foundation to the biorhythm theory," says Halberg, a professor of medicine at the University of Minnesota. "It holds that biological cycles are the same for everybody and the same for all of their lifetime. Its origins are silly. It's a numerological scheme. It contradicts everything we know about biological rhythms, with their dozens of variables from person to person."

Chronobiology, on the other hand, involves detailed study of the changes in people's internal functions—such as brain waves or pulse. "We find cycles in every system of the body," explains the Austrian-born Halberg, 59. "Many more can be discovered, measured and eventually exploited. From the timing of a meal to the administration of an anticancer drug, working with, instead of against, the body's rhythms can tip the scale between health and disease, and even between survival and death."

Halberg says the theory can be applied even to individual cells. "By charting rhythms of cell division in healthy and in cancerous tissue," he argues, "it should be possible to find the time when chemotherapy or irradiation is least harmful to healthy cells." Experiments along this line at several universities have led Halberg to conclude that "chronotherapy can double the cure rate of leukemia in mice."

The potential applications in fact extend to virtually every organ. "Here lies a beautiful challenge," Halberg says enthusiastically. "Find out how to eat, and how to work to optimize life span and performance."

Halberg himself works 100-hour weeks, and his last vacation, about 20 years ago, was only two days long. (Like many scientists," says a colleague, "Halberg is obsessed.") After World War II he moved from Innsbruck to Harvard, where he began studying the effects of cortisone on mice. He transferred to Minnesota in 1949 and met his future wife, Erna, now 58, a medical technologist who was also from Innsbruck (though they had not known each other there). They were married the next year. "I was very scared," Erna remembers. "He was so dedicated. I didn't know if I'd be strong enough. He said: 'You'll have to do everything in the house.' "

Erna runs the household, scans a dozen medical journals for chronobiology-related news and whenever her husband brings home a clutch of visiting scientists, she whips up a big dinner (variations on beef tenderloin are a specialty). A heavy traveler, Halberg this past summer visited labs in France, Germany, Italy, Japan, Belgium and Alaska. Once, in danger of missing a flight, he ran to the gate, banged on the door and shouted, "Open up! I've got an international chronobiology meeting in Washington!" After he was seated on the plane, he pulled charts from his briefcase and immediately began to lecture the passengers on either side of him.

The author or co-author of more than 500 scientific papers, Halberg has also given the English language the adjective "circadian," meaning "rhythmic biological cycles of about a day," as in the normal sleep schedule. (Many cycles recur at near-24-hour intervals, but others vary widely. Last year a man in a joint Harvard-Montefiore Hospital experiment, for example, created his own 38-hour day when completely isolated, sleeping 16 hours and staying awake for 22.)

When the professor began his research into chronobiology, it was called "Halberg's paranoia" by unbelieving colleagues. Even today he faces some skeptics who doubt the importance of cycles. Halberg's response is to work even harder to win converts to his cause. His days in the lab frequently run from 7 a.m. to 10 p.m., and when he is trying to hire new researchers, a friend notes, "He has been known to imply that until this moment they have been wasting their lives."