People who have frequent sex are generally healthier. Most health benefits seem to be linked to penile-vaginal intercourse.

Frequent sex may also bring longer life, fewer coronary events, lower blood pressure. Nardini and her husband, a professional photographer, initially decided to have sex like bunnies with the hope that all the activity might help them overcome his-and-her bad habits: cigarettes and chocolate, respectively.

And indeed, the nightly trysts did help. But they also found, unexpectedly, that frequent sex made them feel better in other ways, too.

Nardini says they both slept better and had more energy, and she didn't get a cold or the flu all month as she usually does in the winter.

"Sex doesn't seem at first glance to be the cure for what ails you, but there's so many health benefits of having more sex," Nardini says. "Anyone can be better served by having more sex."

In fact, the experiment was so successful, the couple plans to have daily sex in January, too.

Researchers have long known that not only is sex fun (when done with the right person, of course), but that people who have frequent sex tend to live longer and have healthier hearts and lower rates of certain cancers.

These studies also show that men with an active sex life have healthier sperm, and sexually active women have fewer menopause symptoms.

A healthier heart

In a British study, people who had intercourse twice a week or more were less likely to have heart attacks and other fatal coronary events.

Those who had sex less than once a month had twice the rates of fatal coronary events, compared with those with the highest frequency of intercourse.

Lower blood pressure

In a study published in the journal Biological Psychology, people who had sex more often tended to have lower diastolic blood pressure, or the bottom number in a blood pressure reading.

Brody's experiment, in which more sexually active study subjects had markedly less dramatic blood pressure spikes when they were put under stress, also supports the benefit.

Lower risk of breast cancer

A French study found that women who have vaginal intercourse not at all or infrequently had three times the risk of breast cancer, compared with women who had intercourse more often.

Lower risk of prostate cancer

A Minnesota study found that men who'd had intercourse more than 3,000 times in their lives had half the prostate cancer risk of those who had not.

While it's not clear why this would be true, studies have found that men who had more intercourse tended to have better prostate function and eliminated more waste products in their semen.

"These differences could conceivably impact prostate cancer risk," Brody writes in his article.

Pain relief

Whipple and others have conducted studies suggesting that more sexual activity helps relieve lower back pain and migraines.

A slimmer physique

A study of healthy German adults revealed that men and women who had sex more frequently tended to be slimmer than folks who didn't have as much sex.

Sex burns 50 to 60 calories per encounter, Whipple says, so sex three times a week for a month would burn about 700 calories or the equivalent of jogging about seven miles.

Better testosterone levels

A group of men being treated for erectile problems saw greater increases in testosterone when, along with the treatments, they had frequent sex.

Specifically, men who had sex at least eight times per month had greater increases than those who had sex less than eight times per month.

* Fewer menopause symptoms Menopausal women in Nigeria experienced fewer hot flashes when they had sex more frequently.

Brody says this may be because sexual activity c helps regulate hormonal levels, which in turn affect r the symptoms of menopause.

Healthier semen

In three studies, men who had frequent intercourse had a higher volume of semen, a higher sperm count and a higher percentage of healthier sperm, compared with men who tended to participate in other sexual activities.