Lead author Caitlin Mason of the Fred Hutchinson Cancer Research Center in Seattle says the yearlong study involved 439 overweight-to-obese, sedentary, post-menopausal Seattle-area women, ages 50-75, who were randomly assigned to one of four groups -- exercise only, diet only, exercise plus diet and no intervention.
The study, published in the American Journal of Clinical Nutrition, found those who lost 5 percent to 10 percent of their body weight -- approximately 10 to 20 pounds for most of the women -- through diet and/or exercise saw a relatively small increase in blood levels of vitamin D. But women who lost more than 15 percent of their weight experienced a nearly three-fold increase in vitamin D -- independent of dietary intake of the nutrient.
"Since vitamin D is generally lower in persons with obesity, it is possible that low vitamin D could account, in part, for the link between obesity and diseases such as cancer, heart disease and diabetes," Mason says in a statement. "Determining whether weight loss helps change vitamin D status is important for understanding potential avenues for disease prevention."
Vitamin D promotes calcium absorption and is needed for bone growth and bone healing influences cell growth, neuromuscular and immune function and reduces inflammation, the National Institutes of Health says.