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Felipe Fossati Reichert, Jonathan Charles Kingdom Wells, Ulf Ekelund, Ana Maria Baptista Menezes, Cesar Gomes Victora and Pedro C. Hallal

Background:

Physical activity may influence both fat and lean body mass. This study investigated the association between physical activity in children between the ages of 11 and 13 years and both fat and lean mass.

Methods:

A subsample of the 1993 Pelotas (Brazil) Birth Cohort was visited in 2004–2005 and 2006–2007. Physical activity was estimated through standardized questionnaires. Body composition (ie, fat and lean mass) was measured using deuterium dilution. Those with moderate-to-vigorous activity greater than 420 min/wk were classified as active, and physical activity trajectory was defined as being above or below the cutoff at each visit.

Results:

Four hundred eighty-eight adolescents (51.8% boys) were evaluated. The mean difference in fat mass in boys and girls who reported ≥ 420 min/wk of physical activity in both visits compared with those who were consistently inactive was –4.8 kg (P ≤ .001). There was an inverse association between physical activity and fat mass among boys in both crude and confounder-adjusted analyses, whereas for girls, the association was evident only in the crude analysis. There was no significant association between physical activity and lean mass.

Conclusion:

Physical activity may contribute to tackling the growing epidemic of adolescent obesity in low- and middle-income countries.

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Felipe Fossati Reichert, Ana Maria Batista Menezes, Jonathan Charles Kingdom Wells, Ulf Ekelund, Fabiane Machado Rodrigues and Pedro Curi Hallal

Background:

Prospective studies on physical activity (PA), diet, and body composition in adolescents are lacking, particularly outside high-income countries.

Goals:

To describe the methods used to assess these variables in the 1993 Pelotas (Brazil) Birth Cohort and to discuss the fieldwork challenges faced and alternatives to overcome them.

Methods:

In 2006–07 a subsample of the 1993 Pelotas cohort was revisited. PA was estimated using questionnaires, a combined heart-rate and motion sensor (Acti-Heart), and the ActiGraph GT1M accelerometer. Diet was investigated by questionnaire. Total body water was determined by stable isotopes. Thirty individuals had their total energy expenditure assessed by doubly labeled water. All data were collected at participants’ home.

Results:

The logistics of the fieldwork and the difficulties in undertaking the study and alternatives to overcome them are presented. Preliminary analyses show that 511 individuals were traced (response rate = 90.0%). Compliance of both adolescents and their families for the motion sensors and body-composition measurements was excellent.

Conclusions:

The authors conclude that it is feasible to carry out high-quality studies on PA in developing countries. They hope the article will be useful to other researchers interested in carrying out similar studies.