In this study, we will provide supplemental vitamin D in postmenopausal overweight/obese women, and hypothesize that it will not affect areal BMD, but will alter bone compartments (trabecular and cortical bone). In addition, higher vitamin D intake will increase serum 25OHD and suppress serum PTH and bone turnover during weight reduction. Secondary outcomes include the influence of vitamin D and weight loss on markers of insulin resistance and on cognitive tests of attention, learning, and memory.

Inclusion Criteria:

• Body mass index of 25-40 kg/m2
• Postmenopausal
• Age 50-72 years

Exclusion Criteria:

• Women who are taking any medication known to influence Calcium or bone metabolism,
• Evidence of diseases known to influence Calcium metabolism (i.e. metabolic bone disease)
• hyperparathyroidism
• untreated thyroid disease
• significant immune disease
• hepatic disease
• renal disease or a kidney stone in the last 5 years
• significant cardiac disease
• active malignancy or cancer therapy within the past year