Physical activity and fat mass gain in Mexican school-age children: a cohort study

The MVPA (5-d accelerometry), BMI, FM and FFM (air displacement plethysmography) were measured at baseline and endline. Associations between gains in BMI, FM and FFM and changes in MVPA were examined using lagged and dynamic regression models, controlling for energy intake and demographic variables.A total of 205 children were analyzed. Gender affected the effect of MVPA on FM gain. In girls, a high baseline MVPA predicted a lower FM gain (-0.96 kg, p=0.025) compared to low/medium MVPA. Increasing, decreasing or having a persistently high MVPA predicted a lower FM gain (range -1.6 to -1.03 kg, p<0.05) compared to persistently low MVPA. In boys, increases in MVPA were associated with higher gains in BMI (+0.76 kg/m2, p=0.04) and FFM (+1.1 kg, p=0.01) compared to persistently low MVPA.These results support a protective role of MVPA on FM gain in girls, suggesting that it may play a crucial role in the development of obesity. Further research on the gender effect of MVPA is warranted to better understand its role in the prevention and control of overweight and obesity.Childhood obesity is an alarming public health problem worldwide [1]. The negative consequences of obesity include short and long-term social and economic consequences and emotional and pathophysiologic complications at individual level [2,3]. In México, the summed prevalence of overweight and obesity in children was 24.3% at 6 y of age and 32.5% at 12-y of age [4], representing a difference of 12.2 percentage points, the largest during elementary school.Lack of physical activity is assumed to be an important contributing factor in the development of childhood obesity [5,6]. Many studies have investigated the association between objectively measured physical activity and obesity in children; however results have been inconsistent [7,8], probably due to inadequate measurements of physical activity and body composition [9] or study design flaws [8]. It has been proposed that physical activity intensity may