Objective: To determine prospective changes of body fat among school adolescents in an interval of 10 years (1997-2007). Method: The study is a longitudinal (Trend). The scholars were selected in a probabilistic (stratified) in five provinces of Maule Region (Cauquenes, Linares, Constitution, Curicó and Talca). The sample size of 1997 was 236 (129 boys and 137 girls) and 253 2007 (140 boys and 113 girls). Ages ranged from 11.0 to 14.9 years. Variables were assessed weight, height and 4 skinfolds. Results: No changes in weight, height, BMI and arm folds (Bi+Tr), however, in relation to body fat in the central region of the body (Sb+Si) showed significant differences (p<0,001) adipose tissue in both sexes and at all ages.sults portend increased adipose tissue in the central region of the body during adolescence at least until 2007. Conclusion: We determined prospective changes in body fat among schoolchildren of both sexes. The results portend increased adipose tissue in the central region of the body during adolescence at least until 2007.