Effects of weight loss on serum 1,25-(OH)2-vitamin D concentrations in adults: A preliminary report

Summary During a review of 42 metabolic studies in healthy women and men we observed that serum 1,25-(OH)₂-D concentrations were directly correlated to the observed daily changes in body weight (r=0.68;P<0.001) and to caloric intake/kg/day (r=0.39;P=0.01). These relationships could not be accounted for by related and physiologically expected changes in serum Ca or iPTH concentrations. However, serum 1,25-(OH)₂-D concentrations were observed to be inversely correlated to serum PO₄ levels (r=−0.44;P=0.004). In addition, serum PO₄ levels were inversely correlated to the daily changes in body weight (r=−0.40;P=0.009). Since dietary sodium intake averaged 142 mmol/day, it is unlikely that the observed changes in weight were the result of changes in salt and water balance. Thus it seems reasonable to speculate that serum 1,25-(OH)₂-D concentrations may vary directly with energy balance, as reflected by changes in body weight. This effect may be mediated by alterations in PO₄ metabolism. The accurate assessment of serum 1,25-(OH)₂-D levels thus appears to require several measurements over time periods during which body weight is stable.