The Relationship Between Iron Status and Free‐Living Physical Activity in Indian School Children

Abstract

Iron deficiency affects many functional outcomes such as maximal oxygen uptake, energy efficiency, and work productivity. Physical activity is a functional outcome that is less well understood due to inherent difficulties associated with its measurement. The objective of this study is to analyze the relationship between iron status and measures of free‐living physical activity in Indian children (12 to 16 years old) during a two‐hour period of discretionary time after school. Physical activity data were collected from the children for one week using Actigraph GT3X accelerometers. Energy expenditure was calculated in metabolic equivalents (METs) from accelerometer counts using Crouter's refined two‐regression model. Energy expenditure was analyzed in relation to iron deficiency (defined as serum ferritin < 12 mg/dL), age and gender using generalized linear models. 64 of the 215 students analyzed in the sample were iron deficient based on serum ferritin levels. Iron deficient participants spent a lower percentage of the discretionary time period at activity levels greater than 3 METs (13.8%) compared to non‐iron deficient participants (16.8%) (p=0.037) when accounting for age. While significant, this effect seems to be confounded by the relationship between gender and physical activity. Iron deficiency in Indian children is associated with a lower percentage of time spent at moderate‐to‐vigorous physical activity levels during discretionary time. Future analyses will be used to examine the relationship between changes in iron status from low doses of iron in biofortified pearl millet and changes in physical activity. Funded by HarvestPlus.