Can seemingly trivial details such as the length of your fingers and whether you wear high heels actually be important clues about your risk for serious medical conditions?
According to Dr. David Agus, author of the new book "The End of Illness," finger length and shoe type are two potentially important pieces of information people can use to unlock their body's secret code. By learning to interpret the body's signals, Agus says people can prolong their health and live their lives free of illness.
"The end of illness is closer than you might think," Agus, also a professor of medicine at the University of Southern California Keck School of Medicine, wrote in the introduction to his book. But to achieve that, he continued, people must look at their bodies in a whole new way.
"Medicine today is, 'I treat the individual condition. Your joint hurts, I'll give you something to help the joints.' But I want to figure out why. What in your system allowed that joint to hurt. And I want to change the whole system in a different direction," Agus told ABC News.
In the book, Agus offers much medical advice he believes people should carefully consider, and there are many recommendations on gathering information that may never have seemed important before, such as the color of the fingernails. While patients should not consider these indicators definitive indicators of illness, he said taking note of them may help patients and their doctors determine next steps in terms of diagnostic tests.
"All these tickers, I want all that data put together before you go to your doctor," he said.
Some of the tips, he says, may seem contrary to what the medical establishment has long recommended, but are important because they show how every part of the body plays a role in maintaining good health. For example, he talks about what it could mean if unpolished nails are a certain color or if people notice they are losing hair near their ankles.
Not all agree that these indicators are always relevant. Doctors in preventive medicine who were not involved in writing Agus' book say while some of the advice he offers is thought-provoking, current scientific evidence suggests these risk factors may not be issues upon which people should necessarily focus.
Still, Agus, who has garnered numerous accolades and is widely know as a cutting-edge figure in medicine, said these seemingly minor signs may offer clues to overall health. On the following pages are some of Agus' hidden health indicators he said people need to be aware of, and how medical experts weigh in.
"If you're a woman, and, for example, you look at your ring finger and index finger, there's data," Agus told ABC News. "And this is a real published study showing that if your ring finger is bigger than your index finger, you're almost twice as likely to get osteoarthritis."
In the book, Agus cited a 2008 study in the journal Arthritis & Rheumatism that found an association between longer ring fingers and higher testosterone exposure in the womb, which lowers the levels of estrogen, a hormone critical to bone development.
In men, Agus wrote that the pattern is reversed -- if the index finger is longer than the ring finger, the risk of developing prostate cancer drops by a third.
The issue of finger length has been a subject of study in the past. A sub-study of the very large and well-known Framingham Heart Study did find a difference in finger length among women with osteoarthritis, and researchers said that arthritis could account for the length discrepancy.
Some experts say that this means a person already has osteoarthritis, not that a person is going to get it. Dr. Sharon Bergquist, assistant professor of medicine at the Emory University School of Medicine in Atlanta, said there have been a number of studies that found a link between finger length and the condition, but the data do not suggest having a longer index finger causes osteoarthritis.
"Even if there is an association, what does it imply from a preventive standpoint, because you can't change the length of your fingers," she said.
But she added that if there are well-established factors present for osteoarthritis, such as being older, being a woman, being sedentary and having other conditions such as gout, an underactive thyroid or diabetes, people can make lifestyle changes such as building up muscle and maintaining proper posture that can prevent the disease from happening in the first place.
Although nails often get attention only as part of a beauty regimen, Agus said they can hold vital health clues.
"Discolored nails can signal certain conditions, from a simple infection to diabetes," he wrote. "If your nails have a yellowish hue to them, it's time for a diabetes check."
Previous research has found diabetes can cause yellowish nails, possibly due to diabetics' inability to properly break down sugar. Thus, the finding of yellowed nails could be a clue that testing for diabetes is in order.
But those with yellow nails must bear in mind that this does not necessarily mean they have diabetes.
"I know many people with diabetes that have normal-colored nails, and people with yellowish nails that don't have diabetes," said Dr. Robert Schwartz, chair of the Department of Family Medicine and Community Health at the University of Miami's Miller School of Medicine.
Nails can become yellow because of other conditions, such as lung disease or heart disease, which cause a lack of circulation to the extremities, fungal infections and age. As people age, the nails can get thicker and grow slower, leading to a susceptibilitiy to fungal infections. Many smokers also have yellowed nails.
Agus also notes a lack of the white crescent normally present above the cuticle can signal a problem with low iron levels.
Hair is another part of the body that can harbor hidden health signs. Graying and baldness can certainly indicate aging, but what about finding hair where it's never been before, or losing hair in previously unnoticed places?
"Have you lost hair around your ankles? This could be a sign of a circulatory problem, especially noticeable in men," Agus wrote.
Circulatory problems can indeed cause men and women to lose hair around their feet and lower legs. But those concerned about unusual hair loss should also be aware that it could also be due to something else.
"In men, most of the time they're wearing very tight socks that can cause hair loss," Scwartz said.
According to the National Institutes of Health, excessive hair growth, known as hirsutism, can indicate a medical issue, but it often has no cause at all and can be hereditary.
But it can also be a result of a hormonal imbalance. Women, Agus said, often start growing hair on their face or arms, which could mean hormonal changes.
Polycystic ovary syndrome, caused by multiple cysts in the ovaries that lead to an excess of male hormones, is one cause. Cushing's syndrome, characterized by an excess of cortisol that causes a sex hormone imbalance, is another possible cause. Obesity, tumors and certain medications can also cause hirsutism.
Women who favor high heels have probably noticed how much their feet and legs hurt after a long day of wearing them, but Agus says the risk to women is much greater than aching feet.
"Aching feet means inflammation. Inflammation in the long term is bad for heart disease, for cancer, for neural degenerative diseases. We want to prevent inflammation," Agus said, calling heels and platform pumps "hidden, sneaky sources of chronic inflammation."
The idea that uncomfortable shoes could lead to problems beyond strained muscles and joints is a controversial one.
"Chronic inflammation can affect the heart. It can lead to an increase of C-reactive protein that is associated with heart disease, but this isn't necessarily caused by wearing high heels," said Schwartz.
"High heels definitely pose more of an issue with the musculosketal system," said Bergquist.
According to Agus, too much sitting can be just as unhealthy as smoking.
"Researchers at the American Cancer Society released a study published in 2010 in the American Journal of Epidemiology that pretty much said sitting down for extended periods poses a health risk as 'insidious' as smoking or overexposure to the sun," Agus wrote.
He cited one study that found women who reported sitting for more than six hours a day outside of work were 37 percent more likely to die than those who sat less than three hours a day. Other research, he added, has linked sitting to obesity, type 2 diabetes, cardiovascular disease and an unhealthy diet.
It's not so much the sitting, he explained, it's the physiological processes sitting causes that are the big culprits.
Even if people exercise once a day, sitting too much can cause increased blood sugar, higher blood pressure and higher triglyceride levels, all linked to cardiovascular disease, obesity and other chronic problems.
And the negative health impacts of sitting is a topic on which many health experts agree.
"The lack of physical activity is the root cause of many diseases," said Bergquist. "It's important to be active and continually move."