Can you have hot sex forever? No problem—just stick to a careful diet, regular Pilates and the miracles of modern medicine. At least that's the message we're getting from the recent burst of celebrity cougar mania and new advertising campaigns from pharmaceutical companies promising that hormones will restore our aging bodies to their former glory. But is it reasonable for women over 50 to expect the same level of sexual satisfaction and drive as a 25-year-old? And is this what women really want?

On one level, just asking these questions represents progress. In Victorian times, for example, doctors routinely warned midlife women to abstain because intercourse past menopause could be fatal. The exact mechanism for this predicted demise wasn't always clear, but physicians of that era did believe it was dangerous for older women to even think about sexual activity because erotic thoughts might, among other evils, evoke regrets for lost allure and those regrets could trigger disease. Medical literature and popular culture of the time (mostly written by men, of course) often portrayed women over 50 as borderline insane. The supposed reason: they were no longer appealing to the opposite sex.

But now our role models are women like the experienced stars of "Sex and the City," who are set to film yet another sequel featuring numerous scenes of Kim Cattrall (52), Sarah Jessica Parker and Kristin Davis (both 44) and Cynthia Nixon (43) enjoying their time beneath the sheets. In the fall, a 45-year-old Courtney Cox will star in ABC's "Cougar Town" flashing a body that any 20-year-old would envy. And then there are those photos of newly svelte Valerie Bertinelli (49) flaunting her toned abs in a bikini. We admire these women for getting out there (especially Bertinelli, who looks incredible).

But frankly, they're all tough acts to follow for those of us without stylists and personal trainers. It's daunting to think that we are supposed to be as interested in sex as we were in our 20s and have bodies and wardrobes that mirror that age. When we were growing up, we rarely saw a college student and her mom wearing the same clothes. These days, that's commonplace—and we're not sure it's such a good thing.

What's needed is a reasonable balance between old-fashioned stereotypes and modern hype, combined with a new understanding of what sex means to women of "a certain age." By the time they reach their late 40s or early 50s, women should be savvy enough to know that feeling sexy is a state of mind, and that a good man doesn't need a partner to look perfect in lingerie in order for her to be desirable.

But there are certainly very real challenges. Women's bodies change as they get older—no matter how much yoga or liposuction they can afford. A slower metabolism makes staying slim a struggle. That's why the vast majority of American women over 45 are either overweight or obese. In order to enjoy sex, you have to feel that you're sexy. That's not easy if your self-esteem is tied to unrealistic images of eternal youth.

Even for women who maintain a size 4, satisfying sex after 50 can be difficult. In a 2007 University of Chicago study published in The New England Journal of Medicine, half of sexually active Americans aged 57-85—male and female—reported bothersome sexual problems. The biggest issue for women is generally the lack of an able partner, usually because of death, divorce or erectile dysfunction (in spite of Viagra). But even many women with partners struggle to find sexual satisfaction. At some point in their lives, about 20 percent of women experience painful intercourse, a condition called dyspareunia. When this happens to women after menopause, it's often because of hormonal changes in vaginal tissue—hence the ad campaigns for vaginal estrogen. (But don't self-diagnose. Talk to your doctor. The pain could also be caused by another problem, such as infection, an allergic reaction or even an early warning of developing cancer.)

Many women find that their libidos take a nose dive as they get older. Hormones may play a role here, too, but low desire can also reflect how a woman feels about aging, her fitness level, stress, medications she is taking or problems in her relationship. Scientists used to think that men and women experienced sex the same way—in effect, a straight line from desire to arousal to orgasm. But now they see female sexual progression as a circle, with many interrelated factors—emotional intimacy, arousal, emotional and physical satisfaction and desire. Men can take a pill to stay aroused and enjoy sex as they get older, but women's responses are far more complex.