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Linking body fat to neurons and energy.

Linking body fat to neurons and energy

Obesity may involve disturbances of the body's autonomic nervous system that cause excessive storage of energy, scientists report this week. They expect their new finding to help undermine the attitude that putting on excessive pounds is "all in the mind," as accumulating evidence links aberrations in basic metabolism to obesity.

The latest study revealed only "weak" associations between body fat and the autonomic nervous system and thus needs to be duplicated. But knowledge that the nervous system could be directly involved will help physicians identify different types of obesity and individualize treatment, says Hugh R. Peterson of the University of Louisville in Kentucky. He says the new results complement two recent studies showing that inheriting a slow metabolism can lead to obesity (SN: 3/5/88, p.152). "We're probably looking at a metabolic phenomenon related to the autonomic system that is important [in controlling weight]," he said in an interview.

The autonomic nervous system is responsible for many of the body's unsung functions, such as temperature regulation and heart rate. It is divided into the sympathetic and parasympathetic systems, which can be distinguished by hormones and other factors. In general, sympathetic nerves respond during stress and activate energy-using responses such as utilization of stored fat, while the parasympathetic system usually conserves energy through reactions that include slowing the heart rate.

It appears that activity levels of both systems are inversely related to increasing fat in humans, says Peterson. He and other researchers from the university, the Veterans Administration Medical Center in Louisville and the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., report their results in the April 28 NEW ENGLAND JOURNAL OF MEDICINE. Earlier animal studies found that decreased sympathetic activity may cause excessive fat storage while increased parasympathetic activity may prompt overeating -- both leading to obesity.

But in their study of 56 healthy but overweight men, the authors found to their surprise that both systems appear to be depressed. The depression in parasympathetic activity may be the body's attempt to slow weight gain, and responsible for different weight plateaus, Peterson says. "It's likely that [the two systems] do not turn on and off as an entire unit, and that they turn on and off in different organs at different rates," he says. Because the observed decreases in activity were small, Peterson says more studies must be done to confirm the relationship -- including studies during weight gain and loss, to learn whether the autonomic changes are the causes or effects of obesity.

Scientists still have only a partial picture of obesity, says Peterson. "It looks as though an explanation of human obesity in terms of psychosocial factors is inadequate," he says. "But I don't think we've reached the point where we can say those factors are not important."
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Title Annotation:links between obesity and autonomic nervous system
Author:Edwards, Diane D.
Publication:Science News
Date:Apr 30, 1988
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