The research is published in the April 7, 2009, print issue of Neurology ?®, the medical journal of the American Academy of Neurology.

It is estimated that 5-10 percent of adults in the United States have RLS and the disorder often has a substantial impact on sleep, daily activities and quality of life.

For the study, researchers questioned 65,554 women and 23,119 men, all of whom were health professionals who took part in the Health Professionals Follow-Up Study or the Nurses' Health Study II. None of the participants had diabetes, arthritis or were pregnant. Of the groups, 6.4 percent of the women and 4.1 percent of the men were identified as having RLS.

The research found men and women with a body mass index (BMI) score over 30 were nearly one-and-a-half times more likely to have RLS than people who were not obese.

In addition, people who were in the top 20 percent of the group for highest waist circumference were more than one-and-a-half times more likely to have RLS than the bottom 20 percent of the group with the lowest belly size. The results were the same regardless of age, smoking, use of antidepressants or anxiety.

"These results may be important since obesity is a modifiable risk factor that is becoming increasingly common in the U.S.," said study author Xiang Gao, MD, PhD, with the Harvard School of Public Health in Boston. "More research is needed to confirm whether obesity causes RLS and whether keeping a low BMI score and small waist size could help prevent RLS."

Gao says some studies suggest that obese people have lower dopamine receptor levels in the brain. "Since decreased dopamine function is believed to play a critical role in RLS as well, this could be the link between the two." Dopamine is a chemical naturally produced by the body that transmits signals between nerve cells.

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Those who displayed a limited ability to delay gratification were 29 percent more likely to be overweight at age 11. The association was partially explained by mothers' weight status. "The influence of maternal weight status on child weight reflects genetic as well as environmental factors, such as feeding patterns and availability of food," the authors write.

Parenting techniques may be available to help children develop an ability to delay gratification, the authors note. "Some strategies that have been described in prior studies have been keeping the desired item (in this case, food) out of sight (and therefore out of mind) or distracting the child's attention from the food to another engaging activity. Another possibility is simply providing a logical structure to snacks and mealtimes such that the child learns that food is not to be eaten the moment it is desired, but to wait until the next snack or meal time," the authors write.

(Arch Pediatr Adolesc Med. 2009;163[4]:297-302, 303-308.

"Can a child's self-regulation capacity be changed or is it an innate and immutable human trait?" write Robert C. Whitaker, M.D., M.P.H., and Rachel A. Gooze, B.A., of Temple University, Philadelphia, in an accompanying editorial. "Self-regulation is shaped by both nature and nurture; it is influenced by environments and experiences during early childhood."

"There are not yet any tested 'office-based' interventions for improving children's capacity for self-regulation," they write. "However, there are promising results from randomized controlled trials showing that interventions in preschools can increase children's positive social behaviors."

(Arch Pediatr Adolesc Med. 2009;163[4]: 386-387.

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