Calcium and Lipid Metabolism

The incidence of obesity has rapidly increased in recent years and reached epidemic proportions in the United States. Recent epidemiological data has shown an inverse relationship between calcium intake and body fat and emerging research suggests that inadequate dietary calcium consumption may increase obesity. Studies in mice have shown that an increase in dietary calcium consumption creates a shift in the utilization of energy stores from carbohydrates to fat and a shift in the partitioning of energy from storage (as fat) to expenditure (as heat).

We will give 1500 mg of calcium a day for three months to women who habitually consume low levels of dietary calcium. The following measurements will be made before and after calcium supplementation: body fat by DEXA, lipolysis by infusion of stable isotopes of 1,1,2,3,3-[2H5] glycerol , hepatic glucose production by infusion of stable isotopes of 6,6-[2H2] glucose, lipogenesis by measurement of fatty acid synthase activity (14C radiochemical assay) , mRNA expression ( Real Time Polymerase Chain Reaction) and protein content (ELISA), indirect calorimetry measurement of non-protein respiratory quotient (NPRQ), energy expenditure, fat and carbohydrate oxidation. Serum calcium, glucose, cholesterol, triglycerides, LDL, HDL, parathyroid hormone, leptin, free fatty acids, adiponectin, 1,25(OH)2D, 25(OH)D and urinary calcium excretion will also be measured.

Inclusion criteria

• BMI between 25 and 30 kg/m2
• Taking oral contraceptives
• Having regular menses

Exclusion criteria

• Pregnant
• History of metabolic bone, renal or thyroid disease,
• History of diabetes mellitus, or gestational diabetes mellitus
• Cigarette smoking
• Self-administration of calcium supplements
• Regular aerobic activity, i.e. jogging > 1 mile/day