Estimating the effects of energy imbalance on changes in body weight in children.
BACKGROUND
Estimating changes in weight from changes in energy balance is important for predicting the effect of obesity prevention interventions.


OBJECTIVE
The objective was to develop and validate an equation for predicting the mean weight of a population of children in response to a change in total energy intake (TEI) or total energy expenditure (TEE).


METHODS
In 963 children with a mean (+/-SD) age of 8.1 +/- 2.8 y (range: 4-18 y) and weight of 31.5 +/- 17.6 kg, TEE was measured by using doubly labeled water. Log weight (dependent variable) and log TEE (independent variable) were analyzed in a linear regression model with height, age, and sex as covariates. It was assumed that points of dynamic balance, called "settling points," occur for populations wherein energy is in balance (TEE = TEI), weight is stable (ignoring growth), and energy flux (EnFlux) equals TEE.


RESULTS
TEE (or EnFlux) explained 74% of the variance in weight. The unstandardized regression coefficient was 0.45 (95% CI: 0.38, 0.51; R(2) = 0.86) after including covariates. Conversion into proportional changes (time(1) to time(2)) gave the equation (weight(2)/weight(1)) = (EnFlux(2)/EnFlux(1))(0.45). In 3 longitudinal studies (n = 212; mean follow-up of 3.4 y), the equation predicted the mean follow-up measured weight to within 0.5%.


CONCLUSIONS
The relation of EnFlux with weight was positive, which implied that a high TEI (rather than low physical activity and low TEE) was the main determinant of high body weight. Two populations of children with a 10% difference in mean EnFlux would have a 4.5% difference in mean weight.
Swinburn
Boyd A
BA
School of Exercise and Nutrition Sciences, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia. boyd.swinburn@deakin.edu.au
Jolley
Damien
D
Kremer
Peter J
PJ
Salbe
Arline D
AD
Ravussin
Eric
E
D000293:Adolescent; D000367:Age Factors; D001827:Body Height; D001834:Body Water / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005006:Ethnicity; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008954:Models, Biological; D009765:Obesity / Q000209:etiology / Q000517:prevention & control*; D011237:Predictive Value of Tests