The Saturday Early Show turned to clinical nutritionist Samantha Heller, a contributing editor at Health magazine, to find out whether these drinks can really do the trick for dieters.
"They do not promise what they deliver," Heller said.
"There are so many products on the market that make health claims that the FTC and FDA cannot keep up with them all," she explained. "Much of the 'scientific evidence' upon which these claims are based is either non-existent, wrongly interpreted or are funded the manufacturers of the products."
For example, said Heller, "in some cases the amount of a substance used in clinical studies that may have shown a slight change in weight or fat burning can be 5-20 times the amount in these beverages. You would have to drink 10 bottles or more a day to get even close to those amounts."
To add credibility to their claims, these companies "like to throw around terms like 'thermogenesis,'" said Heller. "Thermogenesis means your body's metabolism revs up for a while and produces heat. The process of thermogenesis takes place every time you eat. The theory is that some products will increase thermogenesis for a long period of time so you burn more calories and fat and will lose more weight. As of now there is not enough scientific evidence to support these claims."
While the drinks are "probably not" harmful - "except to your wallet!" - Heller thinks that people who try them may not realize how highly caffeinated they are; consumed in addition to someone's daily dose of coffee, dieters could find themselves with jittery nerves.
In place of the green tea drinks, Heller had suggestions of other drinks that help curb a dieter's appetite. For instance, green and black tea "contain healthy chemicals called polyphenols, antioxidants, and micronutrients. Teas also contain caffeine. For an 8 oz. cup there is about 30-50 mg caffeine, just enough to give you a late afternoon energy boost with no calories. Add a small snack like a handful of nuts or a small nonfat yogurt and the edge will be taken off your hunger and you'll be good to go for the rest of the day."
She also likes hot chocolate that's made with skim or soy milk ("You also get a good dose of calcium, protein and other essential vitamins and minerals," she said), but, alas, no added whipped cream. You can also simply go for water combined with packets of no-calorie mixes like Crystal Light.
"Sometimes," Heller said, "we confuse hunger with thirst. Drinking a non-caloric beverage that has flavor may help quell those vague sensations of hunger."