also been reported among Puerto Rican males and females and Cuban-American females. Among school-aged children, increases in obesity have been reported among African-American and Puerto Rican girls; Mexican, Puerto Rican, and Cuban boys; and Native Hawaiian boys and girls. Additional information on ethnicity and pediatric obesity is provided by Kumanyika (1993).

ETIOLOGY

Energy Intake

Obesity results from an energy imbalance in which energy intake exceeds energy expenditure. This imbalance can result from excessive energy intake, low energy expenditure, or some combination of both. The relative importance of each of these factors in children and adolescents in causing and sustaining the obese state remains a matter of debate (Gutin and Manos, 1993).

Although there has been considerable debate over the issue of whether the obese consume more calories than the nonobese (Griffiths et al., 1987; Rolland-Cachera and Bellisle, 1986; Stefanick et al., 1959; Sunnegardh et al., 1986), there is little evidence to support this theory, and no general consensus exists. For example, several studies have reported a lack of association between energy intake and body weight in adults (Braitman et al., 1985; Romieu, 1988). With regard to children and adolescents, energy intake (as measured by self-report) does not appear to differ significantly among obese, obesity-prone, and normal-weight youths (Corbin and Fletcher, 1968; Eck et al., 1992; Johnson et al., 1956; Stefanick et al., 1959; Wilkinson et al., 1977). Excessive fat intake has been proposed as a determinant of obesity, and data indicate that obese children may consume more calories as fat than do nonobese children (Eck et al., 1992), although these results remain equivocal (Obarzanek et al., 1994; Rose and Mayer, 1986). In addition, self-report data on dietary intake may not be a valid measure of habitual energy intake (Bandini et al., 1990b; Lichtman et al., 1992).

Indeed, using doubly-labeled water techniques, Bandini et al. (1987) found that both obese and nonobese adolescents underreport habitual energy intake. While the self-report estimates of intake of the obese and lean subjects were similar, the doubly-labeled water results showed that obese adolescents underreported caloric intake by 40 percent, while nonobese adolescents underreported caloric intake by only 20 percent. The doubly-labeled water technology allows researchers to assess energy expenditure of free-living individuals accurately over repeated days. Since obesity can result from even a small imbalance in energy intake, a



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement