Under-reporting of energy intake in women - Reporting of Energy Intake

Nutrition Research Newsletter, Nov, 2003 by F Scagliusi, V Polacow, G Artioli, F Benatti, A Lancha

Valid food consumption data are necessary in nutrition research, especially in epidemiological studies. Evidence indicates that under-reporting is a common error among self-reports of food intake. However, many aspects of this phenomenon remain unexplored. Only a few studies concerning under-reporting have been conducted in developing nations. It is uncertain whether there is a higher degree of under-reporting for some food and nutrients. If under-reporting is selective, it could affect not only absolute values of consumption, but also the relative classification of persons in terms of their intakes, leading to a compound misclassification bias. The aim of the present study was to quantify under-reporting of energy intake in Brazilian women, identify under-reporting of determinants, determine whether there was an indication for selective under-reporting and test if a motivational multi-method training in combination with providing the subjects some results from the prior recording period, was able to reduce under-reporting.

Subjects enrolled in the study included 38 healthy, 13 normal-weight, 13 overweight, and 12 obese women. Three subjects (two normal weight and one obese) withdrew. Age ranged from 23 to 53 years. To be eligible, subjects had to have a BMI of between 18.5 and 35 kg/m2, regular menstrual cycles, a sedentary lifestyle, and were not dieting or practicing restrictive diets. They should also not have lost more than 5 kg in the past year.

Energy expenditure (EE) and resting metabolic rate (RMR) were calculated with heart rate monitoring. Energy intake (EI) was assessed using a seven-day diet record. A basic principle of energy physiology is that if a person is in energy balance, which may be the case if body weight and composition remain stable, energy intake must be equal to energy expenditure. So, to identify under-reporting, energy intake (EI) was divided by EE (EI:EE) and by RMR (EE:RMR). EE:EI less than 1 for a person who did not lose weight in a four-week period was considered under-reporting. Reporting accuracy was defined as EI-EE.

Seventeen subjects (49%) under-reported their energy intake. Five subjects (14%) reported energy intakes lower than RMR. Six women (17%), one normal-weight and five overweight, over-reported their intake. A negative correlation was found between social desirability and EI:EE. During the focus group, a great part of the subjects, especially the overweight and obese women, said they felt ashamed of their intakes, especially of sweets and snacks. This feeling made them under-eat during the recording period. Some obese volunteers said that the record made them more conscious of their diets and they tried to correct their faults by eating fewer sweets and snacks and more fruits and vegetables.

Subjects tended to report their intake in a socially desirable way. Inclusion of social desirability score as a covariate in studies that rely on self-reports of food intake may be useful. A motivational training program, developed in such a way that subjects feel comfortable reporting intakes of foods considered socially undesirable, in combination with confrontation with earlier results of dietary assessment and the use of portion size measurement aids can be used by dietitians and researchers to attenuate under-reporting.

F Scagliusi, V Polacow, G Artioli, F Benatti, A Lancha. Selective under-reporting of energy intake in women: Magnitude, determinants, and effect of training. J Am Diet Assoc 103(10):1306-1313 (October 2003) [Correspondence: Fernanda Baeza Scagliusi, RD, University of Sao Paulo, School of Physical Education and Sport, Department of Biodynamics, Laboratory of Nutrition & Applied Metabolism. Avenue Professor Mello Moraes 65, Sao Paulo, Brazil 05508-900. E-mail: feseagliusi@hotmail.com