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.
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 < 30) and obesity (> 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.


METHODS
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%.


CONCLUSIONS
The %BF values associated with BMI classifications of overweight and obesity vary considerably with age in growing children, particularly in girls.
Taylor
Rachael W
RW
Departments of Human Nutrition, University of Otago, Dunedin, New Zealand. rachael.taylor@stonebow.otago.ac.nz
Jones
Ianthe E
IE
Williams
Sheila M
SM
Goulding
Ailsa
A
D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D000293:Adolescent; D001823:Body Composition; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000175:diagnosis* / Q000453:epidemiology; D012016:Reference Values; D012727:Sex Characteristics