The Sex Detective Is In!

You can glean a ton about a guy's libido and reproductive health just by eyeballing him. Harry Fisch, MD, author of Size Matters, reveals how to read the clues.

A guy may talk a big game and wear jeans that are tighter than Adam Levine's, but that doesn't mean he has what it takes to keep up with you in the sack...or get you knocked up when you're ready. The real signs of a highly sexual male are a lot more subtle and surprising. According to urologist Harry Fisch, the following six traits and behaviors indicate that a man is truly made for action.

He's Trim Around the Middle

You've no doubt heard that a dude with a gut is more likely to keel over from a heart attack later in life, but it's also a bad sign in the sexual realm. Testosterone is broken down more quickly in belly fat. So that big stomach? It's literally sucking him dry of the stuff.

"Testosterone is the gas that drives the car," Dr. Fisch says. "If it's low, he's going to be low on gas. He'll be tired, he's not going to be able to exercise very much, he's less likely to be in the mood, and his fertility will be lower because a guy needs a certain level of testosterone to produce sperm."

Waist size is especially a concern if your guy is over 30, when metabolism slows and testosterone levels decrease by about 1 percent each year.

He's Got Guns

If a great sex life is high on your list of priorities, find a guy who's trim and jacked. "Someone who regularly works out and lifts weights is likely to have a higher libido," says Dr. Fisch. That's because the body needs testosterone to build muscle mass, so if he has Mario Lopez-like biceps, he usually has more of the hormone. You can't say the same for men who are "skinny fat" — you know, the tall, thin guy who has a body like a noodle. "If he's too scrawny, he's not going to have a lot of testosterone or a strong sex drive," Dr. Fisch says. "Unfortunately, working out can only boost a guy's testosterone levels to a point, and some men will never build big muscles because they don't have high enough levels."

He Parties Smart

Smoking and heavy drinking have the same effect on a guy's mojo as a Rosie O'Donnell striptease. "Smoking constricts blood vessels, which means there's less blood flowing to his penis," Dr. Fisch says. This may cause him to have problems getting — and maintaining — an erection. Downing more than three drinks also can leave him limp because alcohol is a central-nervous-system depressant, which once again, limits blood flow to his penis. So a guy who knocks back lots of cocktails? He's probably not going to be the life of the party in bed.

His Testicles Are in Top Shape

You can learn even more about a guy's long-term sexual potential once his pants are off. First, check out his testicles: Each should be the size of a walnut, says Dr. Fisch, and they should be nearly equal, though small differences are normal. If one is considerably smaller — say, the size of a cherry — then that's a fertility red flag. Around 95 percent of a testicle is made up of sperm-producing cells, and 5 percent is made up of testosterone-producing cells. A smaller testicle makes for a smaller sperm factory.

While you're feeling around down there, note how heated his boys get. "If his testicles run hot, it could be due to a group of pronounced veins in the scrotum, called a varicocele," says Dr. Fisch. "These veins are filled with warm blood, and the extra heat reduces sperm count." A varicocele can be flat or raised and can look similar to a group of varicose veins in the legs. To find out for sure if he has one, cup his balls and firmly — but gently — run your thumb along the scrotal skin, being careful to check for raised portions or lumps (which may feel like coiled string).

He Has Stellar Semen

You can glean a lot from the volume, clarity, and taste of a man's semen. A guy's ejaculate should be about half a teaspoon. If he's producing less, it could mean he's been ejaculating a lot from sex or masturbation or that he has an infection or blockage of the ejaculatory ducts, Dr. Fisch says.

Semen is mostly fluid, but about 1 percent of it is sperm, which is what gives it a cloudy appearance. If you notice a man's ejaculate has a watery consistency instead of a creamy one, he likely has a low sperm count and he may have difficulty fathering kids. As for taste, "a guy's semen is a mixture of fluid that contains sugar — fructose — from the seminal vesicles and a salty taste from the prostate," Dr. Fisch says. If a man is having sex or masturbating frequently, as in every day or several times a day, he's going to deplete the fructose-containing fluid, so his semen will taste saltier. If he hasn't ejaculated in a while, it's going to be sweeter.

He Takes Just Long Enough

You don't need a PhD to know that a guy who comes too fast can put a damper on your sex life (anything less than 2 minutes is considered premature ejaculation). But a man who takes forever to peak despite being hard also may be cause for concern. For one, he may be giving himself a hand too often. "Some men masturbate so much that they know their trigger points and it becomes more difficult for them to come inside a woman," Dr. Fisch says. It could also indicate that he's on an antidepressant or anti-anxiety medication, which can cause prolonged ejaculation.

Biggest Guy Sex Myths

We felt compelled to clear up some misconceptions.

Despite common belief, the size of a man's hands and feet has nothing to do with the size of his penis.

If a guy is big all around — say, he's a 6-foot-4 football player — that doesn't mean he's going to have a humdinger of a hummer. And a small guy could be very well hung.

A veiny penis does not indicate that a guy has a problem. In fact, it's totally normal.
Hairiness has zero correlation with virility. Men with hairy chests are genetically predisposed to it — it has nothing to do with testosterone. Similarly, if a guy is balding, it's not a sign that his libido will be lacking. In some cases, it actually may suggest that he has more testosterone.

Not every man masturbates regularly. About 5 percent of the male population doesn't do it.