Prevalence of obesity in adolescents and the impact of sexual maturation stage on body mass index in obese adolescents

Objective: Puberty is a high-risk period for the development of obesity. The aim of this study was to determine the prevalence of obesity in adolescents admitted to an outpatient adolescent clinic and investigate the relationships between the increase of body mass index and sexual maturation stages in obese adolescents. Material and methods: We recruited 6,462 adolescents, aged 9-16 years, admitted to the outpatient clinic of our Adolescent Unit, between May 1999 and September 2000. BMI was calculated as weight per height² with weight in kilograms and height in meters. Adolescents with a BMI ≥ 95 th percentile for age and sex were defined as obese, with BMI's ≥ 90 th percentile but < 95 th percentile were defined as overweight and considered at risk for obesity. Obese adolescents, with endocrine problems identified to cause obesity, were excluded from this study. Pearson correlation coefficients were used to assess the relationships between BMI and age. The differences between the sexual maturation stages were evaluated with Mann-whitney U Test. Results: Out of 6,462 cases screened, 151 obese adolescents were found. Prevalence of obesity for the total sample surveyed was estimated at 2.3%. BMI values were significiantly correlated with age in both sexes. In girls, only the increase of BMI values from stage I to stage II was found to be statistically significant. In boys, BMI values did not differ significantly between the sexual maturation stages but the number of obese cases were high in stages I and II. Discussion and conclusion: The pubertal growth spurt (timing determined by sexual maturation stage) effects the amount of fat accumulation and the distribution of fat in different ways in boys and girls. So, not only the age and sex but also the sexual maturation stage has to be taken into account while evaluating the BMI values for investigating the risk of obesity in puberty.