(HealthDay News) — For obese Americans who are deficient in vitamin D, taking a supplement of the nutrient might help them lose weight, new research suggests. The study was to be presented Thursday at the European Congress on Obesity in Prague.

Luisella Vigna, MD, of the University of Milan, and colleagues studied 400 overweight and obese people with vitamin D deficiency who were put on a low-calorie diet and then divided into three groups. 

One group took no vitamin D supplements, while the two other groups took either 25,000 international units (IU) or 100,000 IU of vitamin D per month.

After 6 months, participants in both the 25,000-IU group and the 100,000-IU group had lost more weight (–3.8 kg and –5.4 kg, respectively), as compared with no vitamin D supplementation (–1.2 kg). 

The 25,000-IU and 100,000-IU groups also had greater reductions in their waistlines (–0.4 cm and –5.48 cm, respectively) than those who hadn’t taken the supplements (–3.2 cm), Vigna’s team found.

Improvements in HbA1c were observed in the 100,000-IU group, but the result wasn’t statistically significant after adjustment for weight loss.

“The present data indicate that in obese and overweight people with vitamin D deficiency, vitamin D supplementation aids weight loss and enhances the beneficial effects of a reduced-calorie diet,” Vigna’s team said in a European Congress on Obesity news release. 

The researchers suggest that all overweight and obese people should have their vitamin D levels tested. Previous studies have suggested that about 40% of North American adults are deficient in vitamin D.


  1. Vigna L et al. Abstract T8:PO.110. Presented at: European Congress on Obesity; May 6-9, 2015; Prague, Czech Republic.