President Obama has mentioned many times that the health reforms he is proposing will not alter the health care of those who already have health insurance and want to keep what they have. But this is NOT the view of most practicing physicians - myself included. I may be one of the most vocal, but I am not alone.

1. First of all, there is a critical and growing shortage of primary care physicians. Only about 2 percent of the current medical school graduating class is going into primary care. Those of us who already practice primary care are overwhelmed and many are quitting. The public insurances have the most trouble. Surveys show that 50 percent of doctors don't take Medicaid, and in 2008, the Medicare Payment Advisory Commission found that 28 percent of Medicare patients looking for a primary care physician couldn't find one. This problem will only get worse under any Obama plan. You may have new government-provided insurance, but you may not be able to find the doctors who take it. And if you do, they may be buried under a pile of paperwork, or be too busy changing over to the new Electronic Medical Records system to spend time with you.

2. More than 150 million Americans have employer-provided health insurance. But if there is a public option, your employer may stop providing you with insurance. You may be compelled to take the public option, which will probably provide you with less real health care choices.

3. If the public option grows bigger, because private insurers find they can't compete, expect care to be rationed, as the government makes choices to try to contain costs. Reimbursements to doctors will be cut, as they have been under Medicare and Medicaid, but also, you may not be able to get dialysis if you are over a certain age, or you may have to wait on long lines for procedures, as they do in Canada.

4. Bottom line - extending a system that already has too few primary care doctors who are overworked to the entire population does not bode well for prevention or quality of medical care. The costs will continue to spiral upward, and access will decrease rather than increase. A better approach would be to work on re-organizing the health care system towards prevention rather than intervention BEFORE expanding it. One way would be to pay for the education of primary care doctors and create a task force to treat the uninsured.

For more on my take on public health insurance and how doctors view it, check out my opedin Monday's NY Post.

Dr. Marc Siegel 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 the 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"and "Bird Flu: Everything You Need to Know About the Next Pandemic." Read more at www.doctorsiegel.com

Dr. Marc Siegel, a practicing internist, joined FOX News Channel (FNC) as a contributor in 2008..