It's been a stressful two years for Barack Obama. He’s campaigned nonstop, day-to-day, hour-to-hour, flying to different states and sleeping in different time zones. He's also had to fight off the typical character attacks and mudslinging that hit any candidate for office.

And, on the eve of the election, his grandmother, a woman he credits for helping to raise him, died of cancer.

As studies have shown and many a doctor has seen with his own eyes, stress takes a toll on the body. It can lead to premature aging, heart disease, stroke, high blood pressure, depression and cancer.

So how old is Obama? Biologically, he’s 47 years and 3 months old. But a program called Realage.com says his "true age" is at least 49 years and 8 months old. The Web site claims it can calculate your "true age" based on a myriad of factors, including how often you visit your doctor, what your vital signs are, how often you exercise, what you eat, what your extracurricular activities are, and how much stress you have in your life.

There are many unknowns concerning Obama’s health. What is known is that he’s been a smoker on and off for many years, he’s African American, he’s middle aged and, as his doctor attested to in a statement released earlier this year, he’s in excellent physical condition.

At 6-foot-1, his estimated weight is 160 pounds. And his blood pressure, 90/60, is extremely low.

Realage.com takes into account everyday stress and the recent death of a loved one as factors in computing someone's “real age.” But, not surprisingly, campaigning to become president of the United States is not one of choices on the site’s check list.

It’s safe to assume, however, that running for the nation’s highest office takes a toll.

“There’s really no way to tell biological age,” said Dr. Marc Siegel, a FOX News contributor. “The graying that’s developed around his ears ... is that a sign he’s aging? Maybe. George Bush certainly looks older. And Clinton was surviving on a junk-food diet and needed a heart operation after he left office.”

There’s no doubt that stress takes a toll on politicians. Even Obama’s seemingly flawless rhetoric appeared to be suffering on Election Day when, while campaigning in Florida, he asked for support from the people of “Ohio.”

“We know that stress is not only acute, but also chronic,” Siegel said. “It’s cumulative. It wears you down. If there’s an increase of stress hormones over time, there’s also an increased rate of disease. The combination of stress and smoking is distressing for Obama. But he’s thin, he’s robust and seems to be in good shape.”

Dr. Keith Ablow, a psychiatrist and FOX News contributor, said stress causes lapses in memory and other mental impairments.

“I would tell anybody, whether they are an entrepreneur or politician, that you can incur a debt if you go short on sleep for weeks or months or longer,” he said. “You can come to a place where your short-term memory is impaired, attention span and judgment is impaired. That said, we’d expect someone who captures the nation’s highest office would have a plan to manage that kind of schedule and deficits.”

Ablow said a lack of sleep can cause mood swings, irritability and reduced fluency with language. It can also cause speech patterns to change.

“The other side of this is the tremendous side that fuels you,” Ablow said. “The motivation and elation weigh in on performance and function. [Obama] is probably running on adrenaline right now. Whatever stress he had before is resolved. He’s been elected. He feels relief.”

“We really don’t know how much of Obama’s momentum is driven by adrenaline,” Siegel said. “Everyone’s different so you also have to take into consideration how high your adrenaline level is compared to your cortisol level.”

The stress hormone cortisol can be offset by adrenaline.

Preparing for the Presidency

Obama has several weeks during which he can wind down and revitalize before heading to the Oval Office.

“He has to exercise,” Siegel said. “It’s a boring answer, I know, but it increases the positive hormones in your brain, the anti-stress hormones in the brain, and triggers a physiological response to offset stress.”

Siegel and Ablow said Obama also must try, hard as it may be, to get back to life as usual.

On Wednesday, the day after he won the election, Obama gave the appearance of trying to do just that.

He began his first full day as president-elect by having breakfast with his daughters, an everyday family activity that he often had to sacrifice during his campaign. He also exercised at a friend’s home.

“His physical and psychological well-being depends on level of exercise, diet, genetics and outlook on life,” Ablow said.

Obama still has a lot on his plate. He needs to figure out when to move his family to Washington and who will serve in his cabinet, and he also has to make funeral arrangements for his grandmother.

“Losing his grandmother is a tremendous stress,” Siegel said. “It’s his grandmother that brought him up, or at least helped bring him up in a household without a father. To lose someone this close right before this election is an enormous load on top of the stress of the campaign.”

To heal, Siegel said, Obama should spend time with his family and core of friends.

“I would advise that he spend less time with crowds of 90,000 people and have more at-home dinners,” he said.

Ablow also issued this warning:

“The biggest health risk for Barack Obama is whether he returns to smoking. That may have been how he handled things in the past. Hopefully it isn’t how he handles it in the future.”

FOXNews.com health editor Jessica Doyle contributed to this report.