With nearly two-thirds of America's adult population now classified as either overweight or obese, the health implications of "over-nutrition" are growing as rapidly as the nation's collective waistlines.

At UC Davis Health System, bariatric surgeon Mohamed Ali directs the minimally invasive/robotic surgery and bariatric surgery programs, where he focuses on the most challenging patients — those who continue to be dangerously obese after repeatedly trying and failing to control weight.

Ali has performed some 400 bariatric surgeries since arriving at UC Davis nearly three years ago. National trends have shown the number of procedures have skyrocketed — from about 16,000 in the early 1990s to more than 103,000 in 2003 — as the prevalence of obesity has increased and the procedure has become safer.

In addition to a busy surgical practice, Ali runs an active research program. UC Davis is one of six centers in the U.S. chosen by the National Institutes of Health to be part of the Bariatric Surgical Clinical Research Consortium, which conducts multiple projects as part of its Longitudinal Assessment of Bariatric Surgery program.

Ali is assessing a pre-surgery behavior modification program to determine if it enhances weight loss and maintenance after a bariatric procedure. He is also collecting and analyzing a number of factors in patients who have undergone bariatric surgery, including metabolic indicators, energy expenditure, satiety hormones and behavioral choices leading to unbalanced nutrition.

He is hoping that such information, little of which has been collected previously, will provide insights into weight loss and maintenance of healthy body weight following weight loss surgery.

"Currently we are using the best treatment for this difficult medical problem," says Ali. "But we have to constantly strive to improve outcomes."

UC Davis professor Judith S. Stern, who has published extensively on obesity and weight loss issues, is approaching the problem from a different angle — unsubstantiated claims in dietary supplement advertising. When she heard about "Fat-Trapper Plus"™ and how its key ingredient, chitosan (a product derived from shellfish), purportedly reduces fat absorption and helps people lose weight, she designed a simple, inexpensive study to see if the claims were true.

She asked eight men and 12 women to follow a customized diet and gave them the product as directed by the manufacturer. She then analyzed fat excretion in their stools and compared it to levels during control periods without the product. The results: "Fat-Trapper" trapped nothing but people's money. Two subsequent studies with other chitosan products, "Absorbitol" and "Fat Magnet," resulted in similar conclusions.

Those selling dietary supplements often back up their claims with purported scientific research, and Stern is eager to help other scientists, policymakers, and the public more easily distinguish science fact from science fiction. To facilitate these goals, she co-directs the Collaborative Obesity Research Evaluation Team (CORET), an international joint effort between UC Davis and the Nutrition Institute at the University of Maastricht in the Netherlands. CORET consists of a global team of nutrition experts to establish criteria for evaluating published research in nutrition. The group plans to post on its Web site current and relevant reviews of published literature on obesity that fulfill the group's criteria.

"Just because something is published, doesn't mean it's important or good for public policy," says Stern. "CORET will be instrumental in disseminating only high-quality scientific information that scientists and the public can draw from with confidence."

Dennis Styne, chief of pediatric endocrinology, is especially worried about the youngest — and most quickly growing — group of obese Americans: children. Probably nowhere is the problem more acute than in the Native American community, where almost half of children have a body mass index above the 85th percentile and more than 28 percent are above the 95th percentile.

"When we approach a problem that affects such a large segment of the population, we cannot use the medical paradigm of diagnosis and treatment of disease," says Styne. "An extensive prevention strategy is clearly the most important."

With the help of generous contributions from the Rumsey Band of Wintun Indians, Styne is developing a program targeted to the unique needs of the Native American community. He is training tribal members to use the weight management programs he has already developed for children and teens — incorporating their own culture, images and traditions.