But while they agreed that the drink, in principle, would work to burn extra calories, these experts stopped short of glowing reviews when it came to their impressions of the overall health effects of the beverage. Katz, for one, noted that the beverage's claims are still "ahead of the science." And nutritionists had additional concerns.
"There is some evidence that thermogenic beverages have a short-term impact on human metabolism," said Joanne Ikeda, a nutritionist emeritus at the University of California at Berkeley. "However, there is no evidence that anyone has lost weight or maintained their current weight by drinking thermogenic beverages as a component of their diet."
"How long does this thermogenic effect last? Not known," said Keith-Thomas Ayoob, a nutritionist at the Albert Einstein College of Medicine in the Bronx, N.Y., who added that the same effect could be achieved with two cups of coffee and a multivitamin.
"Probably people adapt over time," he said. "Exercise is a better way to jumpstart your metabolism, and it's healthier as well."
And then there is the matter of all of that caffeine. Haley said that the drink, if consumed responsibly, would not cause people to exceed a safe daily level of caffeine. The problem that Haley, too, acknowledges is that no recommended limit for caffeine has yet been established -- and a certain amount of additional caffeine may have varying effects from person to person.
"The concerns are that the caffeine effects can increase heart rate and blood pressure -- presenting hazards for stroke, increasing insomnia, and other ill effects," said Dr. James Anderson, professor emeritus of medicine and clinical nutrition at the University of Kentucky in Lexington.
"The consumer needs to be aware that they are paying a health price and risk for using these drinks," Anderson said. "Is the health risk of drinking three cans worth a pound of weight loss per week?"
On its Web site, the drink already carries contraindications for those who are sensitive to caffeine, pregnant and nursing women, and children. And Haley noted that the company goes above and beyond when it comes to ensuring that consumers are aware of what they are drinking when they reach for Celsius.
"We put the amount of caffeine on our label," he said. "We don't have to, but a lot of other companies don't want that on there."
Haley added that, as with any product, there is only so much you can do to control what people do with Celsius. He said that last week, he was having lunch with some business contacts, and two of the women he met with ordered the beverage mixed with whisky -- a drink they termed "Celsius and Crown."
"That's not what we're about," he said. "You can choose -- and we have chosen -- not to promote it. We've chosen to go the healthy route."