OK. For the past 20 years or so I've spent almost all of my free time trying to whittle my tush, and now I learn big rear ends are desirable. So desirable, in fact, women with small rears are getting actual butt implants, to use the medical term.

One more reason to hate J. Lo, I guess.

It turns out the implants have been popular in South America for years - butts are the breasts of Brazil, as one plastic surgeon put it - and now, like a swarm of killer bees or Krispy Kreme doughnuts, they're moving north.

Yikes. Cover your rears.

Whenever important scientific news like this breaks, my cell phone starts to ring off its charger. Monday, when an implant story ran on WebMD, was no exception.

``Can I donate my butt to someone else?'' one caller asked. ``I'm in a position to be very generous.''

``Why is it people always want the thing they don't have?'' a veteran of every diet and leg squat known to mankind wanted to know.

``What's next?'' another asked. ``Back fat implants? A spare tire implant? A double chin? Bingo arms?''

One can only hope.

As anyone who's considered plastic surgery knows, no procedure - not a lateral eyebrow lift, not a quickie Botox injection, not a belly button touch-up, not an ear tuck - is without risk. The butt implants are no exception.

The surgery, which involves inserting a soft but solid silicone implant in the upper half of the buttock, can result in infection or damage to the leg's sciatic nerve.

One plastic surgeon who performs the procedure told ABC.com the implant is ``not totally comfortable when you sit back on it.''

Those complications sound bad, but the one I'd really fear is disfigurement. Instead of strutting around with a curvaceous, perky rear like J. Lo's, I'd end up looking like one of those ``before'' pictures for a diet aid. I'd be shown from the rear, hanging over the sides of my bikini.

And with my luck, I'd pay the $5,000-per-bun fee (the procedure is not covered by insurance) and then the body-type pendulum would swing. Big butts would go out of style and I'd have to join a class action suit trying to force the butt-enhancement manufacturers to remove the offending implants for free.

(We'll be the ones standing in the courtroom, too uncomfortable to sit.)

When I mentioned the trend to one of my more oblivious friends, he asked whether J. Lo herself has implants. The word on the street is no, but she is rumored to have had her booty insured for $300 million. (Insured against what, I'm not sure. Weight loss, perhaps?)

Though most of the women interviewed for butt implant stories insist they first tried to enhance their butts through exercise, and turned to surgery only after all else failed (all else except gaining weight, that is), I have read one successful workout story.

In 1994, years before J. Lo's rear end became the toast of the world, Melanie Griffith told New Woman magazine that a winter spent snowshoeing up 3,000-foot Aspen Mountain raised her butt three inches.

That number is impressive for two reasons: First, three inches is a lot to raise a butt, and - more importantly - who knew you could measure tush elevation?