Talk about a miracle diet – Katie Couric has become the Incredible Shrinking Anchorwoman.

Thanks to a computer “slight” of hand, the Tiffany network has made the new face of “CBS Evening News” instantly drop about 20 pounds.

In a picture widely distributed to the media last month, a normal-looking Couric wore a frumpy light gray suit and her trademark smile.

But thanks to Photoshop, the popular editing software, the same photo, printed in a CBS magazine, shows her looking much, much thinner – and her suit has become a few shades darker.

Couric, who was made aware of the picture’s alteration yesterday, joked that she liked the original better.

“There’s more of me to love,” she quipped.

The picture was taken in May when Couric, 49, appeared at the CBS “Upfront” presentation at Carnegie Hall.

It was later widely distributed by CBS as an official photo of its new $15 million-a-year anchor- woman.

Then the computer generated version appeared in the latest quarterly edition of Watch!

It’s produced and edited by the CBS press department and distributed to network employees, news-media outlets, affiliates, network gift shops and Paramount-owned theme parks.

Network officials say the magazine has a circulation of around 400,000.

“The picture was retouched without the knowledge of Ms. Couric or CBS News management,” a CBS spokesman said.

As far as the magazine goes, an insider insisted the publication was just following normal industry practice when it shrunk Couric.

He claimed that just about all magazines tinker with photos – even though some top photographers and photo editors at news organizations have lost their jobs in recent times for doing just that.

Most media experts say that whenever a photo is altered in any way, the public should be alerted, although it’s more of a problem if it occurs at newsmagazines rather than a magazine a company publishes about itself.

A top health expert joked that if Couric dropped the weight as rapidly as she appeared to, it would have cost her an arm or a leg – literally.

“Besides Photoshop, the only other way to lose 20 pounds in a matter of seconds would be to hack off a limb,” joked Samantha Heller, the senior clinical nutritionist at NYU Medical Center.

“I mean, liposuction is pretty fast – but that takes longer since you have to prep for surgery and everything.”

On a more serious note, she said, “Of course the healthy way to do it wouldn’t be fast.

“If you lose weight too quickly it scares your body – the body is not designed to lose weight quickly. [Instead], cut back on the junk, pretty standard stuff. Katie could eat more vegetables, cut down on carbs and increase her exercise,” said Heller.

“I know she has a trainer because she talked about it [when she was on ‘Today’] so she could have the trainer pump up her exercise a bit.”