Quantifying Changes in Free-living Physical Activity of Rwandan Women Using Accelerometry Data after an Iron-biofortification Efficacy Trial.

Objectives: To quantify changes in free-living physical activity in Rwandan women before and after a 4.5 month feeding trial of biofortified beans. Methods: 145 Rwandan women (18-26 years) were randomized to receive either iron-biofortified beans or traditional beans for 5 months. Blood biomarkers and functional outcomes were measured before and after the feeding period. Free-living physical activity was assessed using the Actigraph GT3X accelerometer which the women wore for 5 consecutive days (3 weekdays and 2 weekend days). Total energy expenditure and metabolic equivalents were calculated. General linear models were used to evaluate the effect of the intervention on energy expenditure during free-living physical activity. Results: 58 women complied with the Actigraph wearing protocol. Women in both the treatment and control groups expended about 500 fewer calories after the intervention controlling for wear time. Change in ferritin in the intervention group but not the control group significantly predicted increased change in kilocalories expended. Conclusions: Changes in iron status from a biofortification trial significantly predict changes in daily energy expenditure.

Effects of an Iron-biofortification Feeding Trial on Physical Performance of Rwandan Women.

Objectives: To examine the effects of an iron-biofortified bean intervention on physical performance in Rwandan women assessed by VO2max and work efficiency. Methods: 145 Rwandan women (18-26 years) were randomized to receive either iron-biofortified beans or traditional beans twice daily for 5 months. Blood biomarkers and physical performance were measured before and after the feeding period. VO2max and work efficiency at 70 watts were assessed with a mechanically braked cycle ergometer (Monark 874E). Heart rate, O2, and CO2 were directly measured with the Cosmed K4B2 system. Non parametric tests and mixed effects models with repeated measures were used to evaluate the effect of the intervention on blood biomarkers and VO2max and work efficiency. Results: Serum ferritin significantly increased in the iron-biofortified group (4.0 μg/l increase in median in treatment group, 2.5 μg/l increase in median in control group; p=0.04). VO2max significantly increased in the iron-biofortified group compared to the control group (p=0.05). Work efficiency at 70 watts significantly increased over time but was not different between groups. Conclusions: Consumption of iron-biofortified beans significantly improved serum iron status and VO2max in Rwandan women but had no effect on work efficiency.