Changes in Iron Absorption and Availability Before and After Weight Loss in Obese Pre-menopausal Women and Men.

Until now adiposity has been associated with low iron status and with higher hepcidin levels. Moreover, weight loss and thereby loss of fat mass, has been associated with decreased hepcidin levels and improved iron status. However, until now no direct measures of iron absorption or incorporation into erythrocytes have been assessed before and after losing weight/fat mass. We hypothesize that: * body fat loss in obese women and men will improve iron absorption, corrected for iron status, from a labeled test meal measured by using a stable isotopes technique by on average 30%. * body fat loss in obese women and men will decrease the related inflammatory state. * greater subclinical inflammation in obese women and men will be correlated with a decreased incorporation of iron into erythrocytes, and that this will improve after loss of body fat. The study is a prospective cohort in which iron bioavailability will be assessed in obese women and men before and after weight loss and associated loss of body fat over a period of 6 months. Iron absorption will be estimated using stable-isotope techniques where incorporation of 57Fe and 58Fe into erythrocytes is measured 14 days after administration. Preparation of isotopically labelled iron will be done at the Laboratory of Human Nutrition of the Swiss Federal Institute of Technology Zurich (ETH Zürich). A baseline venous blood sample will be drawn 6-8 weeks after the surgery when surgery-related inflammation has been resolved. The subjects will receive a test drink, containing 6 mg of 57Fe labelled ferrous sulphate. One hour later, 2 ml of an aqueous solution containing 100 μg 58Fe as iron citrate in 250 cc of normal saline will be infused over 50 min. This infusion protocol has been used safely and successfully to examine iron metabolism in both adults and infants. Fourteen days later, a second venous blood sample will be drawn. This procedure will be performed at baseline (6-8 weeks post-surgery) and at the end of the study (6 months post baseline). Our study could provide important information to establish the mechanism by which obesity-mediated inflammation could induce iron deficiency. This will be the first human trial that will evaluate if the obesity-related reduction of iron absorption is reversible in a context where obesity and iron deficiency are both highly prevalent.