True enough beauty lies within, but don't for a minute let that fool you into thinking that nothing needs to be done on the outside to stay healthy and live a longer, happier life.

Charla Krupp, the style advice expert and author of the book, "How Not To Look Old", says that too many women over 40 look OL'' -- shorthand for ''Old Lady'' -- with their rimless glasses, flat hair, heavy eyeliner, matte foundation . . .

I'll add my own personal observations and bring that number down to 35.

What these women need is a serious makeover.

"Dress less finished, and you'll look younger," says Sharyn Soleimani, personal shopper extraordinaire at Barneys New York. "When you're very young, you can be very finished and you still look young. But when you're more mature, imperfection looks so much better." If you're going to a casual dinner party at a friend's home on a Saturday night in the summer, a suit is too much. Ditch the skirt and wear the jacket (or better, a cardigan) with white jeans and strappy sandals. The goal is appropriately casual. Once you unleash yourself from the suit-as-uniform way of dressing, you will feel liberated and look 10 years (or more) younger.

Look, something like 50 million cells die every second on a human body. Things are gonna droop. Others are gonna dimple. Fashion will march forward while we, with bifocals and varicose veins, eventually fall behind. We lost this battle the moment we were born.

Rage, rage against the dying of the light all you want, says Charla Krupp.

You'll find me contemplating the sunset by the pool, the New Yorker and mojito in hand.

But Krupp's not buying it. By her predictions, I won't be able to afford that pool. I may not be able to keep my job much past 40 because I look OL.

''Youth is associated with fresh ideas,'' says Krupp, sitting outside at the Biltmore Hotel during a South Florida book tour.

Krupp makes the case that if you look OL, you appear at odds with society's crosscurrents. You are a faded rose. Desiccated fruit. A goner.

Charla, this is the stuff that makes feminists throw up.

She fixes me with perfectly primped eyes -- no clumpy mascara or thick black liner here.

''I am the most ardent feminist you will find in your entire life,'' she says with fresh intensity. ``I am saying women should be so unapologetic, so fierce, so unambivalent, so intense about conquering the world. And be great looking, too.''

''More women are single in this demographic, and more will live to 100 than ever before,'' she says. ``The economy's in a downturn. People are losing their jobs. They need to reinvent themselves. No one's hiring people in their 50s. They need to look young!''

Apparently, things aren't so dire everywhere. Take France, she says. A certain mystique follows older woman. But here, on this side of the Atlantic, Krupp thinks graying eyebrows can get you booted from the corner office, even if the boss won't come right out and say so.

'In Hollywood, the euphemism is, `You don't have an edge,' '' Krupp says. In the magazine world, she says, it's ``We want someone who can go on TV and sell it.''

Her ideal isn't about wearing a size 6. It's about avoiding the stylistic blunders that mark you as out-of-touch.

"I'm not saying you should look like a beauty queen. But you want to look like you know what's going on in the world.''

In other words, if you're not ''with it,'' as they say, you're ''out of it.'' And being out of it is going to bite you in the butt some day soon. Especially if you don't stop tucking in that blouse.

Krupp's not a maverick. She's not trying to change the world. She sees herself as merely helping us better maneuver through it.

And along those lines, there's not a snowball's chance that she's revealing her age.

''Because it doesn't do me any good,'' she says. ``People are so ageist.''

The Book: Charla Krupp, How Not To Look Old