A: In the June 12, 2009 issue of Science Daily, a University of Minnesota study found that the initial vitamin D level was a good predictor of weight loss during calorie restriction. People with low vitamin D levels had difficulty losing weight, while those with the highest levels lost the most weight. Women should get 400-800 units of Vitamin D from diet, supplements or sun exposure. Low vitamin D levels are a problem in many women because they spend much of their time indoors and are not choosing foods high in vitamin D such as fish and dairy.