If you’ve read health headlines recently, you may think that a pill has been developed to replace exercise, but this isn’t really the case. Dr. Ronald M. Evans of the Salk Institute in San Diego, a noted researcher, has spent many years studying the effects of a cellular protein known as PPAR -delta. Having previously shown that this protein causes fat burning, he and his research group have now discovered that PPAR-delta can be provoked by drugs to increase the production of type 1 muscle fibers rather than the less useful type 2 fibers. This is significant because type 1 fibers contain more mitochondria, the tiny furnace that provides the muscle with its energy. Type 2 fibers, by contrast, are more prevalent in the muscles of folks who are obese, sedentary, or have diabetes.

Evans and his group found that when given a drug known as Aicar, mice increased their exercise endurance by 44 percent in just 4 weeks. When the test mice were given GW1516, they were able to run 75% longer, provided that the drug was combined with exercise. The results were just published in the reputable journal Cell.

Many in the news media have jumped on these findings and begun to speculate that exercise might soon be obsolete, but there are several reasons to be cautious. In the first place, though these mouse proteins are similar to human proteins, mice are not people, and it is not possible to test these drugs for long term safety in mice, since they only live for little more than a year. Even if these pills appear to help heart function, our most essential muscle, there needs to be more study as to how they affect other essential organs including the kidney, liver, and brain.

Exercise itself has many immeasurable effects on the metabolism, and it also has a positive psychological effect that may not be reproducible by a pill. When you exercise, the brain releases endorphins, happy hormones that make us feel good.

Of course GW1516 or Aicar or drugs like them might end up being useful  for patients with disabilities who  cannot exercise, as well as for people who can exercise but need help getting started or building up after months of inactivity. When human trials start, it might be interesting to study these drugs in astronauts , who are faced with long periods of confinement in space.

But there are other concerns. We already have a problem with performance-enhancing drugs in sports, and this could add to it. And it will always be impossible to accurately measure or replace all the hormones released in response to actual exercise, as well as the feeling of wellbeing that ensues.

Marc Siegel MD is an internist and associate professor of medicine at the NYU School of Medicine. He is a Fox News Medical Contributor and writes a health column for LA Times, where he examines TV and movies for medical accuracy. Dr. Siegel is the author of False Alarm: the Truth About the Epidemic of Fear (Wiley 2005) and Bird Flu: Everything You Need to Know About the Next Pandemic (Wiley 2006). Read more at www.doctorsiegel.com

Last week, Dr. Ronald Herberman, director of the University of Pittsburgh Cancer Institute issued an advisory to his faculty and staff about the potential health risk of cell phones. He cautioned limiting the length of conversations, keeping the phones away from the head by text messaging and using headphones or speaker phones. Why is Dr. Herberman, a reputable cancer expert, concerned, when several large epidemiological studies in Europe and the United States have shown no association between cell phones and brain tumors?

Some reasons to be concerned:

     - A recent Danish study looking at women who used cell phones in the 1980s, when cell phones were much bigger and emitted more radiation, were more likely to have children with neurological or psychiatric problems than non-cell phone users.

     - Since cell phones have only been in common use for a decade, long term safety has not been established despite the fact that there are now more than 200 million cell phone users in the U.S. alone.

     - An ongoing multi-center trial in 13 European countries examining the cell phone use of more than 5,000 people with brain tumors appears to show an increased incidence in brain tumors in those who used cell phones. Further, the side of the brain affected appears to correlate with the side the cell phone was used.

Some reasons not to be concerned:

     - Cell phones emit radiofrequency waves, which lie on the scale of intensity somewhere between the radio waves emitted by your car radio and your microwave. RF waves have been well studied in animals and have NOT been found to damage cells or cellular DNA, generally considered a necessary precursor for cancer.

     – The overall body of evidence is still far on the side of no correlation between cell phone use and health problems including cancer. The epidemiological studies are relatively weak, and firm conclusions cannot yet be drawn.  NO study has shown a cause and effect, meaning that cell phones have NOT been shown to actually cause health problems in any specific cases. In the Danish study described above, for example, the increase in children who are developmentally delayed among women who used cell phones may have had more to do with the lifestyle choices of the cell phone using group, rather than the cell phones themselves (they may have been more anxious, slept and ate more poorly, drank more coffee, etc.)

What to do?

     - Long term studies need to be done, especially the most powerful kind – double blinded randomized trials which can really try to establish a cause and effect between frequent cell phone use and possible health risks.

     – In the meantime, overblown fear of cell phone use will do far more harm than good by creating an unnecessary distraction. People who talk while driving are already at greater risk of having an accident, and worrying about your cell phone will only increase that risk.

     – Cell phones are a key part of an unhealthy lifestyle. Americans these days are far too sedentary; we spend thousands of hours a month at our computers, or on our cell phones and BlackBerries, talking and texting. Even if the small amounts of radiation won’t kill us, the inactivity certainly might.

Marc Siegel MD is an internist and associate professor of medicine at the NYU School of Medicine. He is a Fox News Medical Contributor and writes a health column for LA Times, where he examines TV and movies for medical accuracy. Dr. Siegel is the author of False Alarm: the Truth About the Epidemic of Fear (Wiley 2005) and Bird Flu: Everything You Need to Know About the Next Pandemic (Wiley 2006). Read more at www.doctorsiegel.com