It sounds too good to be true, and it may well be.
Researchers reported this week at a conference in Milwaukee that a cream whose active ingredient is used in prescription asthma drugs can reduce the fat on women's thighs.
The number of women studied is small -- only two dozen -- and the research is highly preliminary, but the obvious appeal of such a seeming wonder drug set obesity researchers buzzing.
The research was done by specialists at Stanford University, Harbor-UCLA Medical Center in Los Angeles and the Pennington Biomedical Research Center in Baton Rouge, La.
They studied two groups of 12 women who used different doses of a cream containing a substance called aminophylline.
Each woman used the aminophylline cream on one thigh and a look-alike inert cream on the other, without knowing which was which. After five weeks, the treated thighs in one group had shrunk in circumference by an average of one-half inch, Dr. Frank Greenway of the Harbor-UCLA, Medical Center told the Associated Press.
In the second group, a less potent cream, used to prevent skin irritation, produced even better results: a reduction of about 1.5 inches in thigh girth.
The cream has been patented and licensed to an entrepreneur, according to Dr. Greenway, who spoke at the annual meeting of the North American Association for the Study of Obesity. Earlier in the conference, other researchers said they had found a natural brain protein called galanin that triggers a craving for fat and another called enterostatin that blocks it. Blocking the first or administering the second can cut body weight in animals by 50 percent, they said.
Fat cells on thighs and on the abdomen are different, said Dr. Ahmed H. Kissebah, an endocrinologist at the Medical College of Wisconsin and organizer of the conference. Dr. Kissebah, in a telephone interview, said his team discovered that fat cells on thighs do not release fatty acids as fast as abdominal fat cells do in response to stress or diet.
This is probably because fat cells on thighs have an unusually high number of receptors called alpha-2-adrenergic receptors. Receptors are molecules that sit on the surface membranes of cells to help other molecules get inside.
"When stress comes, these cells don't release fatty acids," Dr. Kissebah said. Aminophylline may promote release of fatty acids by boosting a different kind of receptor on fat cells called beta receptors, which act in opposition to alpha-2 receptors.
But Dr. Kissebah stressed that a cream to reduce fat thighs "is not just too good to be true, but it's difficult to imagine how it works because it has to go through all these layers of tissue . . . to the fat cells. I really would say this is something that needs to be considered, but we really do need more and better studies."
Dr. Greenway, who shares the patent with one of his collaborators, Dr. David Bray, director of the Pennington labs, said the cream could be available as a cosmetic. Dr. Bray was unavailable for comment.
Betsy Adams, an FDA spokeswoman, said that aminophylline is available only by prescription. She added that it is not clear whether marketing the cream as a cosmetic would allow promoters to sidestep the drug approval process. No matter how such a cream might be marketed, she said, if a product is found to have harmful side effects, the FDA can take action against it.