Nervy approach to fighting fat

It isn't yet known whether either procedure will have a lasting effect on body weight. The body's ability to adapt to a weight loss therapy and find other ways to gain weight has doomed many initially promising anti-obesity drugs. VBLOC tries to prevent the body from adapting to it by using intermittent, rather than constant, blocking of the nerve, Knudson says. Since vagotomy can't do this, obesity researchers such as Dr. Samuel Klein of the Washington University School of Medicine in St. Louis predict it may produce only temporary weight loss.

Lustig, however, cites earlier studies that found that weight loss from vagotomy was sustained for up to 25 years and says that most of his patients have not regained lost weight after 18 months.

Both approaches are being conducted only in clinical trials for now. If the VBLOC study goes well, the device is likely to get Food and Drug Administration approval within two to three years, Knudson says. Vagotomy, since it is a surgical procedure, does not need FDA approval, but the EndoVx device for snipping the vagus nerve would need to be approved, and this could take several years, Lustig says.

For now, the only really effective therapy for severe obesity is weight loss surgery, Schauer says. "But perhaps in five or 10 years we may have a minimally invasive procedure that is just as effective."

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A more sympathetic strategy?

Disabling the vagus nerve slows down energy storage in fat tissue. Another surgery may make the body burn fat faster.

Such a procedure would target the sympathetic nervous system, which regulates fat burning -- as opposed to the parasympathetic nervous system (including the vagus nerve), which regulates energy storage. Some researchers believe that stimulating certain sympathetic nerves could promote weight loss by burning off more calories from fat tissue. "It is like getting the effect of exercise without having to do real exercise," says Dr. Jiande Chen, a gastroenterologist at the University of Texas Medical Branch at Galveston.

Clinical evidence for this idea is lacking, Chen cautions, but indirect support comes from studies on dogs, cats, rabbits and other animals. For instance, in a 1998 study on hamsters at Georgia State University in Atlanta, Timothy Bartness and co-workers found that cutting the sympathetic nerves to part of an animal's fat tissues prevented its body from burning up the energy stored there. Unlike the remaining fat tissues, the "denervated" tissue did not shrink even when food intake was decreased. This suggests that stimulating the nerves instead could have the opposite effect -- of promoting fat burning.