Excerpt: "Why Do Men Fall Asleep After Sex?"

From the guys who wrote the smash hit "Why Do Men Have Nipples?" comes another book bound to answer the questions that most people are too shy to ask.

In "Why Do Men Fall Asleep After Sex?: More Questions You'd Only Ask a Doctor After Your Third Whiskey Sour," writer-physician duo Mark Leyner and Billy Goldberg tackle issues from the universal -- "Why can we still not cure the common cold?" to the obscure -- "Can you breastfeed with fake boobs?"

Smart, funny and informative, the latest installment from Leyner and Goldberg is far more enjoyable -- and much less embarrassing -- than a trip to the doctor could ever be.

Read an excerpt from "Why Do Men Fall Asleep After Sex?" below:

Why do women pee more than men?

Any man who has taken a long car trip with a woman truly believes that women need to pee more than men. As we speed down the highway and begrudgingly pull into another rest stop, we wonder whether this is the result of a genetic difference, obsessive water consumption, or a vicious plan to throw us off schedule.

If you happened to be leafing through the February 5, 2005, edition of The Journal of Urology, you could begin to find an answer. Doctors reviewed twenty-four-hour "urinary diaries" of both men and women and recorded fluid intake and urinary frequency. They found that women do pee more often than men but not because they drink more. In fact, men generally have higher fluid intake but don't need to go as often. When men finally feel the urge, they tend to pee in higher volumes than women. This is because men have a larger bladder capacity. That means smaller bladders in the ladies. Women are also more likely to suffer from overactive bladder syndrome which makes them go even more. No wonder the line is always longer at the ladies' room.

Diaries and memoirs are a red-hot genre these days. There's The Diary of Anne Frank, Che Guevara's Motorcycle Diaries, The Personal Memoirs of Ulysses S. Grant, Karrine Steffans' Confessions of a Video Vixen, and, of course, James Frey's A Million Little Pieces. But, if you're inspired by literary ambition, and decide to keep and then publish your Urine Diary, be aware that it will most probably be classified as "nonfiction." You must account accurately for each and every drop, with absolutely no embellishment or hyperbole. Remember -- if you fib in your Urine Diary, it could really piss off Oprah.

Why do women have smaller feet than men?

Overall, women are smaller than men. The "why" is an evolutionary question that is too complex for us to answer here. But the ways in which men and women differ anatomically is more approachable. Male and female feet differ in size relative to stature. Men of the same height as women tend to have longer and wider feet.

When you compare a male and female foot of the same size, the woman's foot will have a higher arch, a shallower first toe, a shorter ankle length, and a smaller instep. Women also have larger calf circumferences.

Women seem to have an incredible knack for disregarding the shape of their feet and forcing them into ever smaller and pointier high heels. This callous disregard makes the foot differences between the genders even greater by ultimately changing the natural shape of female feet. In 1993, it was reported by the American Orthopedic Foot and Ankle Society that 88 percent of the women surveyed wore shoes smaller than their actual foot size. No wonder our wives are constantly patching their traumatized feet with Band-Aids and tape.

Are men better than women at math?

Danger! Danger! Answering this question incorrectly may force us to sleep on the couch with our wives beating us with the infamous Teen Talk Barbie that was programmed to say, "Math is hard!"

Harvard University president Lawrence Summers stepped into this minefield in 2005, when he suggested that biological differences might be one of the reasons that fewer women are in the fields of science and engineering. His speech led many professors to protest his statement, and others threatened to withhold donations. Several days later, Summers was forced to apologize. And he has since resigned.

So here are some facts (though these are often debated)...

The brains of men and women are definitely different. Women's brains are generally about 10 percent smaller than men's, but this is meaningless when it comes to intelligence. Men and women show no disparity in general intelligence. There are, however, some areas with slight variances. Women are better at visual memory, mathematical calculation, and get better school grades in mathematics. Men, however, are better at mentally rotating shapes, mathematical problem-solving, and score higher on mathematical word problems and on tests of mathematical reasoning.

Whether you agree or disagree on the interpretation of the available data, sociologists generally agree that social factors exaggerated any differences touted in the past. Women are clearly underrepresented in certain scientific fields such as math, engineering, and physics, but women now comprise more than 50 percent of medical students.

In the interest of gender harmony, let's create a new politically correct, asexual Barbie who says something neutral like "Cognitively rotating abstract shapes can be a daunting task -- I prefer mathematical calculation and more linguistically complex and empathy-centered forms of interpersonal communication." Fun!

Why don't women have Adam's Apples?

The Adam's apple is simply a bulge in the human larynx that is made of cartilage. This area is called the thyroid cartilage because it is located right on top of the thyroid gland. If you want to get technical, you can also call it the prominentia laryngea, but Adam's apple is much more quaint, don't you think? It also is not exclusively a guy thing. Both men and women have thyroid cartilage and therefore an Adam's apple. They are about the same size until puberty when increased testosterone causes it to grow more prominent in men.

For some women, the Adam's apple may be larger than desired. But fear not, modern plastic surgery can fix almost anything. All you need is a tracheal shave to reduce the size of the Adam's apple. This sounds like it can be done down at the corner barbershop, but it actually involves making a small incision in the throat and cutting away some of the prominent cartilage. This is one of the most common plastic surgeries for male-to-female transsexuals, unsurprisingly.

So where does the name Adam's apple come from? Most people say that it is from the notion that this bump was caused by the forbidden fruit getting stuck in the throat of Adam in the Garden of Eden. There is a problem with this theory because some Hebrew scholars believe that the forbidden fruit was the pomegranate. The Koran claims that the forbidden fruit was a banana. So take your pick -- Adam's apple, Adam's pomegranate, Adam's banana. Eve clearly chewed before swallowing.

Can men lactate?

You can't write a book called Why Do Men Have Nipples? without getting a question about lactating men. This one came during a radio interview when an irate caller insisted that a man could nurse his own child. We argued with him, but there was no convincing this guy (Benson -- are you reading this?) that it was not possible.

Here is the truth. The mammary glands of human males can produce milk but certainly not enough to feed a child. Usually male milk production is from a pathological condition. The most common cause of man milk is a prolactin-secreting tumor (prolactinoma) in the pituitary gland. Prolactin is a hormone that stimulates milk production. Overproduction of prolactin may be caused by some drugs, including phenothiazines, certain drugs given for high blood pressure (especially methyldopa), opioids, and even licorice. Male lactation is also caused by the hormonal treatments used in men who are suffering from prostate cancer. Doctors use female hormones to decrease the growth of the prostate, but these can also cause milk production or galactorrhea.

Extreme starvation -- by radically disrupting the equilibrium of hormone production -- can also make men lactate (this has been observed in prisoners of war).

It is also possible for males to induce lactation through constant massage and stimulation of the nipple over a long period of time but that sounds like a lot of work. Then there is the fruit bat. Only one male mammal, the Dayak fruit bat, is known to produce milk.

So if you are a male fruit bat with prostate cancer who likes to massage his own nipples, and you happen to be a prisoner of war -- let the nursing begin.

Why do men snore more than women?

In our last book we dispelled the myth that men fart more than women. So what about snoring? In this case the men are guilty as charged. We do snore more for several reasons. To begin with, women have anatomically different airways than men. Women have a wider airway circumference so if there is any obstruction, there's a chance the air passing through will not be as likely to hit the oropharyngeal structures as it would in a man. Additionally, a woman's airway is less prone to collapse than a man's airway, and that works in her favor as far as snoring is concerned.

When men put on weight they tend to put it on around the neck area, whereas women put on weight around the hips. The fatty tissue around the neck literally squeezes the airway closed so air can't pass through smoothly. Air then hits the structures within the throat and vibrates them, which causes the noise we know as snoring.

Smoking and drinking also lead to increased snoring. In general, women tend not to smoke and drink as much as men, and therefore don't suffer the snoring consequences.

Pregnant women do tend to snore more because the blood flow around the nasal area can increase, which causes the lining of the nose and throat to swell. This makes breathing more difficult, so there would be a tendency to sleep with the mouth open, giving rise to snoring.

Why do men fall asleep after sex?

Leave it to a ninety-two-year-old woman to break down a complicated question into the simplest terms. When we told Billy's wife's grandmother the name of our new book, she answered in a second. "Because they work so damn hard!"

As much as we would have liked to settle on that answer, we knew more was needed to make our editor happy. So we scoured the medical literature to try to put this issue to rest. We found studies with fornicating rats, hamsters, and prairie voles, but there was very little direct information about the postcoital snooze. There are many hormonal changes that occur with orgasm and some of these changes may offer an explanation for why men fall asleep.

After orgasm, both men and women release the chemicals oxytocin, prolactin, gamma amino butyric acid (GABA), and endorphins. Each of these contributes to that roll-over-and-snore feeling. They seem to be secreted in equal amounts in men and women, but we all know who orgasms more frequently.

The hormone oxytocin is known to have several effects including establishment of maternal behavior, stimulation of uterine smooth muscle contraction at birth, and stimulation of milk ejection (milk letdown). It is also referred to as "the cuddling hormone" since it tends to elicit the need to be close and bond but not in a sexual way. In one study, oxytocin was shown to inhibit male sexual behavior in prairie voles. Maybe it's the oxytocin that makes us feel satiated and rested after a good romp.

Prolactin is another player in the sex/sleep conundrum. It is produced in the pituitary gland and its best known function is the stimulation of milk production. Prolactin is believed to relieve sexual arousal after orgasm and take your mind off sex. Levels of prolactin rise during sleep and some patients with prolactin-secreting tumors report frequent sleepiness. So prolactin seems like it may be a culprit too.

Gamma amino butyric acid (GABA) and endorphins also both have a calming effect and may make you pass out post-sex.

The tantric answer is that the male orgasm releases outward energy or jing, while the female orgasm is an inward explosion.

Last but not least, we have Grandma's reasoning. It is thought that exertion during sex and after climax depletes the muscles of energy-producing glycogen. This leaves men feeling sleepy. Since men have more muscle mass than women, men become more tired after sex. Also (believe it or not!) women don't always have an orgasm, and that keeps them from producing all those other hormones we just talked about.

Hmmm . . . maybe Grandma was right.

Do men sleep more than women?

Are those men who conked out after sex still asleep?

Actually, some authorities believe that women are biologically programmed to sleep better than men. Estrogen tends to decrease the number of awakenings after you finally fall asleep and also increases total sleep time. Unfortunately, menopause and pregnancy throws off this advantage.

In the Bruskin Research survey of one thousand Americans ages eighteen and older, one of five men ages eighteen to thirty-four concede they take longer than an hour to fall asleep. Also, more than 30 percent of men in that age group admit to falling asleep at work, clearly making up for time lost during their primary nocturnal sleep. As we discussed earlier, snoring and sleep disordered breathing is more common in men than women and this also adds to the dozing dysfunction of men. Researching this one's made me a little sleepy. I think it's time for a nap . . .

Do men have shorter attention spans than women?

We've been trying to answer this question for weeks now, but we can't seem to concentrate long enough to write anything.

One thing that we do know for certain is that attention-deficit hyperactivity disorder (ADHD) occurs primarily in males. The male to female ratio has been reported to be as high as 9:1.

Did you ever notice that...squirrels never fall out of trees...and where do all the dead pigeons go?...uh...wait...weren't we supposed to be answering a question about...what was it...?

Actually, there's no more information about gender differences in attention spans, so you'll have to ponder this one on your own.

Why do women live longer than men?

Life expectancy varies from country to country and people definitely live longer in developed nations than in the third world. But, one of the constants in almost all countries is that women outlive men. In the United States the average life expectancy for men is 74.5 years, while women can expect to be around for 79.9 years.

There are many theories about the reason for female longevity, and since a complete answer would require an entire book, we will try to summarize. There really are two separate questions:

1. Why do men die so young?

2. Why do women live so long?

The available evidence points toward evolution, behavior, and biology. In terms of evolution, women are helped by the need to live long enough to raise their children, while men wear themselves out competing for the right to procreate. Behavioralists point out that around the time of puberty through the twenties, men are three times more likely to die than women. Most of the male fatalities are caused by reckless behavior or violence. In the older age group, behavior-related fatalities are still more common among men. Illnesses related to smoking and alcohol consumption also kill more men than women. Lastly there are some strong biological factors that favor women. Heart disease targets men more readily, and is the main cause of the gender gap in this arena.

The gender discrepancy is most pronounced in the very old. Among centenarians worldwide, women outnumber men nine to one. The good news for the men out there is that if you make it past one hundred, you will definitely have your pick of the litter at the nursing home.