"1 Tip for a Tiny Belly" reads the headline, rendered in fake hand-lettered type and positioned above a crudely animated drawing of a woman's bare midriff. Try as you might to concentrate on something else, the midriff distracts your eye by shrinking and reinflating - flabby to flat, flat to flabby.

"Cut down a bit of your belly everyday by following this 1 weird old tip," it reads. The "weird old tip" is revealed only after you click on the ad.

For months, versions of the ad have been just about everywhere, including such popular websites as Facebook, Weather.com and About.com. They have also shown up on the home pages of news organizations such as the Los Angeles Times, MSNBC, the Washington Post and the Guardian newspaper in Britain.

The ad is so broadly distributed, it's likely you've seen it hundreds of times. The accumulated impressions - the number of times it has flashed by someone on the Internet during the past 18 months - runs into "the tens of billions," estimates Steve Wernikoff, a government lawyer who has tracked it. "It's just a tremendous amount."

The innocent-seeming "1 Tip" ad actually is the tip of something much larger: a vast array of diet and weight-loss companies hawking everything from pills made from African mangoes to potions made from acai berries. Federal officials have said the companies behind the ads make inflated claims about their products and use deceptive means to market them.

The take so far: at least $1 billion and counting.

The "1 Tip" ads are the work of armies of affiliates, independent promoters who place them on behalf of small diet-product sellers with names such as HCG Ultra Lean Plus. The promoters profit each time someone clicks through to the seller's site and orders a free sample. The sample, however, isn't always so free.

In lawsuits filed during the past year, the Federal Trade Commission said the ads are the leading edge of what amounts to a three-step scheme that has conned millions of people.

Much like a barker outside a carnival tent, "1 Tip" is merely a come-on. People who click on the ad are directed to a second site, which looks like a diet or health-news page. The sites go by names such as Consumeronlinetips.com and Weeklyhealthnews.com.

The sites typically feature an article in which an attractive young TV reporter investigates the benefits of a diet involving a series of products. Sometimes the products are made from mangoes or acai berries. In other cases, the products come from human chorionic gonadotropin (hCG), a hormone produced by developing embryos and the pituitary gland.

"We here at Channel 7 are a little skeptical" of the hCG diet, reads the copy at Consumeronlinetips.com. "So we decided to put these products to the test."

In each case, the sites carry favorable blurbs about the diet from well-known news organizations such as ABC, CNN and USA Today, along with brief, laudatory "reader comments."

"I saw this report on TV the other day and was amazed at the results," reads one. "I am getting married next month so the timing couldn't have been better!!"

The pages have links that lead to a third site, where consumers can use a credit or debit card to order samples of the featured products.

Almost everything about these would-be news sites is bogus, the federal government says. It has said the offer of free or low-cost samples is a scheme to capture consumers' credit card numbers, leading to thousands of complaints about unauthorized charges.

In an action aimed at Internet promoters of acai berry products in April, the FTC filed 10 lawsuits against some of the companies and individuals behind the ads. The agency's allegations are nearly identical in each case: that sites such as Consumeronlinetips.com aren't legitimate news organizations, that the defendants can't substantiate the claims of dramatic weight loss and that the sites' operators don't disclose they have financial ties to the diet-product merchants they're linking to.

Although the promoters are apparently unconnected to one another, their sites are remarkably similar. All use what the FTC says are fake articles. Several used the photo of the reporter supposedly investigating the diet. The woman identified as "reporter Julia Miller" on some of the sites is a French newscaster, Melissa Theuriau, who has said she was unaware that her image was being used this way. The endorsements from the real news organizations, such as CNN or ABC, are a sham, too, the government says.

One of the companies the government sued, IMM Interactive of Long Island, N.Y., spent more than $1.3 million last year to place flat-belly ads, which generated more than a billion impressions, the lawsuit says. More than a million people subsequently took the plunge and clicked on the ad, the agency said.

IMM denied almost all of the FTC's allegations in a court filing June 13. But it conceded "defendant does not have sufficient information to admit or deny whether the individuals identified on some of the web pages who claim to have tested the products on themselves and experienced positive results actually tested the products and experienced such results."

The company hedged even further in the fine print of one of its newslike websites, which is cited in the FTC complaint, saying, "This website, and any page on the website, is based loosely off a true story, but has been modified in multiple ways including, but not limited to: the story, the photos, and the comments. Thus, this page, and any page on this website, are not be taken literally or as a non-fiction story."

The FTC says none of the websites can back up its weight-loss claims. But the real heart of the scam, it says, is the free-sample offer. In fact, the sites disclose in fine print that a consumer who hands over a credit card number is signing up for much more.

Someone who orders a sample offered by one hCG marketer, for example, is agreeing to pay an additional $79.99 for another shipment of the product two weeks later, and another $79.99 six weeks after that, the disclaimer says. The charges and the product keep coming until the buyer calls a toll-free number to cancel.

But that's easier said than done, investigators found. Canceling often involved repeated phone calls and frequent hang-ups that left customers frustrated and angry, the agency said. In the meantime, the charges continued to roll on.

The ads haven't gone away, despite the government's sweep of acai berry promoters this spring. Dozens of other affiliate marketers still use the same formula - the teaser ad, the newslike websites, the free-sample offer - to tout hCG and African mango diets. To date, the FTC hasn't taken action against them.