NEW YORK (Reuters Health) - Overweight? Part of the problem may be low vitamin D levels, a new study hints.

Among a group of 90 young women living in sunny southern California, those with insufficient levels of vitamin D were significantly heavier and had greater body mass than their counterparts with sufficient levels of vitamin D, Dr. Vicente Gilsanz, of Children's Hospital Los Angeles and colleagues found.

These findings suggest "obesity is related to vitamin D insufficiency," Gilsanz told Reuters Health.

Vitamin D, which regulates bone metabolism, is mostly obtained through exposure of the skin to direct sunlight. Insufficient vitamin D is thought to impact bone health, and may play a role in obesity.

However, previous studies assessing associations between vitamin D, bone health, and body fat produced inconsistent results, leading Gilsanz's group to examine the relationship between vitamin D levels, body fat, and bone structure among postpubertal women living in a sun-soaked area.

Overall, 37 of the 90 women in the study had sufficient concentrations of the vitamin D metabolite 25-hydroxyvitamin D (30 nanograms per milliliter or above). The remaining 53 women had lesser vitamin D metabolite levels suggestive of vitamin D insufficiency.

"Our study indicates that vitamin D insufficiency is extremely common in young women living in a sun-rich area of the United States," the researchers report in the Journal of Clinical Endocrinology and Metabolism.

There was no association between vitamin D levels and bone measurements in the skeletally mature young women who were between 16 and 22 years old.

However, compared with the vitamin D sufficient women, same-age counterparts with insufficient vitamin D levels were heavier by about 7.4 kilograms (approximately 16.3 pounds) on average. The vitamin D insufficient group also averaged 3.4 points higher in body mass measurements.

Additionally, the investigators say they found an "unexplained and intriguing" positive link between height and vitamin D status. They, therefore, call for further investigation into this, as well as correlations between vitamin D levels, bone growth, and obesity.

SOURCE: Journal of Clinical Endocrinology and Metabolism, January 2009

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