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Energy Intake and Body Mass Index (BMI)
Overweight Women Underestimate Food and Calorie Intake
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Underestimation of Energy Intake - BMI Influence

The validity of estimates of energy intake in a group of young women, and the influence of body mass index (BMI) and concern over bodyweight on such estimates, were determined with the aid of a food record intake. The study subjects were a group of female university students between 20 and 32 years of age. Participants maintained a steady weight over the month-long experimental period. Their energy intake was, therefore, very similar to their theoretical energy expenditure. Discrepancies between intake and expenditure data can be used as an indicator of the degree of over or underestimation of intake. 29.7 percent of subjects had a BMI < 20 kg/m2, 5.5 percent showed BMIs of > 25 kg/m2, and none exceeded the lower limit of obesity (BMI > 30 kg/m2). Of those with BMI < 20 kg/m2, no significant differences were seen between intake and expenditure (-2.3 percent). However, those with BMI > or = 20 kg/m2 showed discrepancies of 10.4 percent. In those with BMI > 25 kg/m2, this figure rose to 22.2 percent Concern over bodyweight, and the amount of weight that subjects wished to lose, increased with BMI (r = 0.72). However, even some subjects with BMI < 20 kg/m2 showed a desire to lose some weight (2.1 +/- 1 kg). A tendency was seen for subjects with BMI > or = 20 kg/m2 to underestimate their food intake. This became more obvious with increasing BMI (r = 0.36). This could mean that obese women habitually underestimate food intake; a factor that could invalidate many dietetic studies published to date. In the present group, when BMI did not exceed 24 kg/m2, mean underestimation was 4.8 percent. However, subjects with BMIs > or = 24 kg/m2 underestimated their intakes by 20.4 percent. Concern over bodyweight (assessed as kg a subject wished to lose) did not change the observed increase in underestimation with rising BMI. Anxiety, therefore, probably parallels true weight and BMI.

Source: Ortega Anta RM, Quintas Herrero E, Sanchez Quiles B, Andres Carvajales P, Requejo Marcos AM, Encinas Sotillos A. Departamento de Nutricion, Facultad de Farmacia, Universidad Complutense, Madrid. 1997

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