(CNN) On Friday, Weill Cornell Medical College offered a seminar to its second-year medical students, one that's been offered only once before.
The focus wasn't cutting-edge pharmacology or modern microbiology but instead, five lecturers exploring different facets of a single topic: "Prescribing the Medicine of Exercise."
This isn't as typical as you might think. More than half of the physicians trained in the United States receive no formal education in physical activity, according to a 2015 study. The study authors discovered that most medical colleges do not offer physical activity-related courses, and the rare exceptions are often electives.
The Weill Cornell seminar, a required class for students, is co-directed by Dr. Jordan Metzl and Dr. Marci Goolsby, both sports medicine physicians at the Hospital for Special Surgery in New York with faculty appointments at Cornell. The seminar teaches medical students how to counsel their patients to exercise, one of the most effective forms of preventive medicine.
"Conceptually, since Hippocrates on down -- which is a number of years! -- medicine has largely been focused on treating illness after it happens," Metzl said. "We spend literally trillions of dollars on treating issues that oftentimes are preventable."
According to Metzl, medicine often just gives "lip service" to prevention, but if you look at the way money is allocated, most is spent on treatment -- not prevention.
Metzl points out that type 2 diabetes, which is largely a preventable disease, ranks among the most expensive disease in the US. Since treating diabetes and all of its complications costs billions of dollars each year, it is time we give more attention to how this chronic disease can be prevented, he said.
The far-reaching effects of exercise work for almost every body system from the brain to the heart, said Metzl, who noted that exercise can also improve memory, concentration and mood while helping lower high blood pressure and cholesterol. Further evidence suggests that exercise has positive effects for many cancer patients and helps control type 2 diabetes.
Exercise is "available to every single person, has zero side effects and works in some capacity for everybody who takes it," Metzl said. "And no drug fits that safety profile with that efficacy."
The US national physical activity guidelines recommend 150 minutes of moderate activity, or 75 minutes of vigorous activity, each week for adults and 60 minutes a day for kids, explains Adrian Hutber, vice president of Exercise as Medicine at the American College of Sports Medicine.
"It's not so much how much a day you need to get but how much a week," Hutber said, though most people break it down to 30 minutes a day. "That's the so-called dosage you would need to prevent or manage many of the common chronic diseases that we have, from hypertension, type 2 diabetes, cardiovascular disease and others as well."
He emphasizes the fact that this is really "physical activity and not exercise." For some patients, "exercise" connotes a gym, and though some people love that idea, others don't.
You can get physical activity by walking the dog, gardening or taking a dance class, Hutber explains, and anything you like to do, you will continue to do.
"Your body doesn't care whether you go to the gym or walk the dog or whatever," Hutber said. "It doesn't know the difference."
Hearing this message from our family physician as opposed to, say, a trainer at the gym is significant, Hutber said. Metzl agrees.
Always an avid athlete, Metzl learned the benefits of exercise firsthand when he developed arthritic pains in his knee as a result of an old injury. Having figured out which exercises improved his pain and mobility, he developed a program, Ironstrength, that is a combination of cardiopulmonary fitness and strength training. He then began teaching others, usually a dozen or so enthusiasts, in basement rooms for free.
Today, Metzl's listserv has grown to more than 32,000 people, and so these days he hosts his (still free) classes for hundreds of people at a shot: children, grandparents, people of all sizes and physical conditions. Based on how he is received, Metzl said, the simple message that "exercise is good for your overall health" seems to carry more weight coming from a doctor.
However, as Hutber notes, though it is distinctly motivating to hear the advice of a doctor in a white coat, the reality is many patients leave the office "with the best of intentions, but unless you have additional support or help, that initial motivation doesn't tend to translate into action."
Another issue is that "physicians traditionally have not been trained in lifestyle medicine, nutrition (or) physical activity in medical school," observed Hutber. So there's a small proportion of doctors with the necessary skills to prescribe exercise, while even fewer have developed a communication style effective enough to help newly inspired patients commit to daily physical activity.
Other medical schools have taken the commitment to exercise even further.
"Right from the beginning, we taught exercise physiology and exercise as medicine across all four years as a requirement for all medical students," said Jennifer Trilk, assistant professor, physiology and exercise science at the University of South Carolina School of Medicine Greenville, which opened its doors in 2012.
Within the program Trilk pioneered at in South Carolina, medical students not only learn the mechanistic aspects of prescribing exercise -- such as how skeletal muscle quality and quantity changes and improves health factors or how exercise effects each of the organ systems -- they're taught behavior change, as well. The lessons are based on well-known standardized models and are adapted to increasing physical activity levels: moving patients from one stage to the next.
"We model it within the curriculum as a requirement from day one," said Trilk, who tells her students: "You are your first patient. You have to stay healthy in order to keep your patient healthy."
Additionally, Trilk has created a classroom-community model by partnering with the Greenville Health System, a health care delivery system with eight hospitals and more than 150 physician offices, and adding US physical activity guidelines into the electronic health records of the system. This means doctors are required to ask patients, for example, how many minutes a day or how many days a week they exercise, to enter into their electronic medical records.
Greenville doctors and medical students track exercise along with chronic, lifestyle-related disease markers and electronically refer patients, when necessary, to "exercise as medicine care coordinators" -- essentially exercise physiologists or other professionals who work with patients on improving their physical activity, explains Trilk.
"I always say to them, 'I'm not teaching you to be exercise physiologists/ I'm teaching you to be good doctors who know how to use your referrals,' " said Trilk, who uses sports metaphors to reach her students. "You are the quarterback, and you're taking the patient, and you're passing that patient onto a qualified individual who can help with behavior change."
In his Cornell seminar, Metzl teaches medical students to be aware of individual patients; prescribing exercise as medicine is not only about the underlying physiology and delivering the message, but about the singularity of each case. One person may be under 30 and obese, another may be a 70-year old heart patient, and many have no access to a gym.
"How do we think about those people differently?" is a key question Metzl asks his students.
Meanwhile, he remains focused on the fact that fixing someone's arthritic knee may also be a "gateway to their physical activity" and so presents an opportunity to use exercise to fix the reason why this knee may have become bothersome in the first place -- and prevent it from happening again in the future.
Still, Metzl acknowledges that exercise is not the only remedy and not the only preventive technique necessary to ensuring good health.
"I'm a Western-trained doctor. I practice Western medicine. I use all the different tools," Metzl said, adding that his kit includes everything from diagnostic tools to pharmaceutical injections. "I don't want to be so far out on the limb that I don't recognize myself."
Trilk also sees prescription drugs as important, necessary and ethically correct in many cases.
"If you've got a patient with uncontrolled hypertension, you may use that medication to start them out for safety reasons," Trilk said, "but you're still counseling them on the benefits of physical activity."
Trik adds that though Hippocrates had his therapies, he also knew the benefits of exercise and diet.
Walking is man's best medicine, he's thought to have said.
"We knew historically that nutrition and exercise were what kept the body well," Trilk added, "and we're finding our way back to that."