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

Abstract

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.