Body fat percentages measured by dual-energy X-ray absorptiometry corresponding to recently recommended body mass index cutoffs for overweight and obesity in children and adolescents aged 3-18 y.

摘要

BACKGROUND: Body mass index (BMI; in kg/m2) cutoffs for use with children and adolescents aged 2-18 y that correspond to the well-accepted BMI cutoffs for overweight (> or = 25 but or = 30) in adults were published recently. OBJECTIVE: The objective was to estimate the percentage body fat (BF) values typically associated with these BMI cutoffs in children and adolescents. DESIGN: The BF was measured by dual-energy X-ray absorptiometry in 661 subjects (49 male) aged 3-18 y. Regression equations using BMI, age, and sex were developed to predict the BF associated with BMI cutoffs for overweight (age-specific BMI equivalent to a BMI of 25 in an 18-y-old) and obesity (age-specific BMI equivalent to a BMI of 30 in an 18-y-old) over this age range. RESULTS: Measurements classified 17.1 of males and 19.8 of females as overweight and 5.5 of males and 7.5 of females as obese. The BF associated with an obese BMI tended to be higher in peripubertal males (34-36) than in younger (24-30) or older (27-30) males. Although the predicted BF of young females was similar to that of young males, values rose steadily with age, such that an 18-y-old female with a BMI of 30 had an estimated BF of 42, whereas that in males of similar age was 27. CONCLUSION: The BF values associated with BMI classifications of overweight and obesity vary considerably with age in growing children, particularly in girls.