Food and beverage giants Nestle and Coca-Cola face a lawsuit by a consumer group that accuses them of making fraudulent claims in marketing and labeling for Enviga, a new artificially sweetened green tea soft drink.

Labeled "the calorie burner" on cans, Enviga is marketed as a weight-loss aid, with claims that it has "negative calories" and that it can "keep those extra calories from building up."

Enviga's web site also says the drink is "much smarter than following fads, quick fixes, and crash diets."

But according to scientists from the Center for Science in the Public Interest (CSPI), Enviga is just a highly caffeinated and over-priced diet soda, and is exactly the kind of faddy, phony diet aid it claims not to be.

The suit was filed in U.S. District Court in New Jersey, part of the region in which the beverage is being introduced.

In December, CSPI served formal notification on Coke and Nestle (and their partnership, Beverage Partners Worldwide) that they would be sued if they continued to use the unsubstantiated calorie-burning and weight-loss claims on Enviga labels and ads, but the company indicated publicly and privately that it had no plans to change the claims.

Enviga consists of carbonated water, calcium, concentrated green tea extract, various "natural flavors," and ingredients typically found in diet soda, such as caffeine -- three diet colas' worth -- phosphoric acid, and the artificial sweeteners aspartame and acesulfame potassium. The company says its green tea extracts are high in an antioxidant called epigallocatechin gallate, or EGCG.

Many of Enviga's claims are based on a 72-hour Nestle-funded study of 31 people who were given a drink containing amounts of EGCG and caffeine equivalent to three cans of Enviga. On average, those subjects expended more energy, according to an abstract of the unpublished study.

CSPI maintains no test of Enviga lasted more than three days. One European study found that EGCG and caffeine did not increase energy expenditure after one month and did not help people lose weight.

One longer-term Japanese study did show that a tea fortified with EGCG and caffeine helped people lose more weight than a control tea, but then again, the study was conducted by a tea company and the subjects of the study were 38 of that company's male employees.

Enviga costs between $1.29 and $1.49 per can, and the company suggests that the maximum effect is gained by drinking three cans a day, or about $1,500 worth of the soda per year.

"There is no clear evidence that what's in Enviga will help you control your weight," said CSPI senior nutritionist David Schardt. "You'd be much better off giving up non-diet soda, which costs nothing to do, or by joining a gym, which is typically less expensive than paying for 3 cans of Enviga a day."