The war against widening waistlines may have a new weapon: Researchers say an over-the-counter hormone supplement might help elderly people shed stubborn belly fat.

Preliminary evidence suggests that increased levels of dehydroepiandrosterone (DHEA), a natural hormone secreted by the adrenal gland, might also help older people keep diabetes at bay.

"The replacement of DHEA, at doses of 50 milligrams per day, brought back DHEA levels in older persons to the range seen in youth. This resulted in a reduction in abdominal fat that was accompanied by an improvement in insulin action," explained study co-researcher Dr. Dennis T. Villareal, an assistant professor of geriatrics and nutritional science at Washington University in St. Louis.

As many middle-aged and elderly individuals can attest, keeping fat from settling around the middle gets tougher and tougher as you age. According to Villareal, abdominal fat also carries special risks to health, since "it's associated with an increased risk for diabetes."

Doctors have long known that belly fat tends to accumulate with aging, just as DHEA levels begin to fall. "DHEA declines progressively with age," Villareal said, "so that when we're 70 years old we only have about 20 percent of the DHEA we had when we were young."

From animal studies conducted in their lab, he and co-researcher Dr. John O. Holloszy suspected that falling DHEA levels might encourage weight gain. So in a double-blind trial, they had 56 non-exercising, elderly individuals take either a 50 milligram-per-day DHEA supplement or a placebo for six months.

Participants taking the hormone supplements lost an average of 6 percent in visceral abdominal fat -- fat deposits lying deep within the abdomen. "It averaged about one kilogram [2.2 pounds] of weight loss per person," Villareal said. Those on placebo experienced no significant weight loss.

Patients on the supplements also made significant improvements in insulin activity, lowering their risk for developing diabetes. That's not surprising, Villareal said, since fatty acids released from abdominal fat cells are known to have a negative affect on insulin action. In terms of health, "what's important is that we saw a specific reduction in abdominal fat, rather than just overall weight loss," he said.

Villareal stressed that it's still much too early to officially recommend DHEA as a weight-loss supplement, however.

"This is only a preliminary study, and we should wait for the results of large-scale, longer studies," he said. "The risks of DHEA haven't been fully defined in this short-term, relatively small study." A larger, five-year trial, involving 176 subjects, is currently under way, he said.

Roberta Anding, a clinical dietitian at Texas Children's Hospital in Houston and a spokeswoman for the American Dietetic Association, called the findings "exciting," adding that they "open up another avenue for the management of obesity."

And she also said that DHEA supplements might even be harmful for people with a history of hormone-sensitive cancers, such as tumors of the breast or prostate. And pointed out that participants in the St. Louis study who took DHEA supplements experienced a "significant" rise in blood levels of estradiol (an estrogen-like hormone) and testosterone, hormones commonly connected to breast and prostate cancers, respectively.

Pending the arrival of long-term further safety data, "there are going to be some people -- individuals with estrogen-sensitive breast cancer, or individuals who may have prostate cancer -- that really should not take DHEA," Anding said.