Obesity has become a major global health problem and at the same time iron-deficiency anemia remains common worldwide. At the individual level these two conditions appear to be linked: overweight persons are at higher risk of iron deficiency than normal-weight individuals. The main objective of this thesis was to understand the underlying mechanism for the association between obesity and iron status.The main findings and conclusions of this thesis are discussed and placed in a public health perspective. Moreover, recommendations for possible future research are provided. Our findings show that overweight and obese individuals present: 1) reduced iron absorption due to adipose related inflammation and increased hepcidin circulation; 2) increased blood volume, diluting serum iron and possibly increasing iron requirements; 3) a suboptimal response on iron absorption when providing ascorbic acid supplementation; and 4) increased iron absorption after fat loss, but only in iron deficient individuals.