Relation of body mass index and body fatness to energy expenditure: longitudinal changes from preadolescence through adolescence.
BACKGROUND
Although it is widely accepted that weight gain results when energy intake exceeds energy expenditure (EE), how reduced EE contributes to the development of obesity remains unclear.


OBJECTIVE
We tested the hypothesis that reduced EE in the premenarcheal period in girls constitutes a risk factor for an increase in relative weight [body mass index (BMI) z score] and percentage of body fat (%BF) during adolescence.


METHODS
We measured EE at study entry in 196 premenarcheal nonobese girls. Resting metabolic rate (RMR) was measured by indirect calorimetry. Total energy expenditure (TEE) was measured by the doubly labeled water method. Activity energy expenditure (AEE) was calculated from RMR and TEE. After the baseline study, girls were followed annually until 4 y after menarche (x+/- SD: 7.1 +/- 2.6 y). At each visit, height, weight, and %BF by bioelectrical impedance were measured. Girls also completed annual food-frequency and activity questionnaires. Linear mixed effects modeling was used to evaluate the longitudinal relation between BMI z score and %BF and measures of baseline EE.


RESULTS
We found no significant relation in change in %BF with RMR, AEE, or TEE. We observed a small positive relation between BMI z score and AEE and TEE (P < 0.05) but no significant relation with RMR. When we stratified by parental overweight, the findings were unchanged for RMR. TEE and AEE were positively related to BMI z score in girls of overweight parents.


CONCLUSIONS
Our findings suggest that EE in the premenarcheal period is not a risk factor for increases in %BF or BMI z score in girls during adolescence.
Bandini
Linda G
LG
Department of Health Sciences, Boston University, Boston, USA. lbandini@bu.edu
Must
Aviva
A
Phillips
Sarah M
SM
Naumova
Elena N
EN
Dietz
William H
WH
D000273:Adipose Tissue / Q000378:metabolism; D001823:Body Composition; D015992:Body Mass Index; D002648:Child; D004032:Diet; D017097:Electric Impedance; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D009765:Obesity / Q000209:etiology