Underreporting of food intake in obese "small eaters"

Thirty sedentary and stable weight obese women were classified as small, normal or large eaters depending on their report of 24 h energy intake (EI) through a dietary history questionnaire. For each subject, resting metabolic rate (RMR) was assessed through indirect calorimetry, physical activity through a self-administered questionnaire and psychological evaluation through psychometric tests. Neither RMR nor indices of physical activity were different between the three groups; however for small eaters, RMR was higher than reported EI (p < 0.001). Thus, the low EI reported by obese small eaters reflected an underreporting of food intake. Psychometric evaluation was not different between normal and large eaters. Small eaters exhibited a better perception of food size than normal or large eaters, and no difference in tests assessing memory or attention; their score (2.8 +/- 1.3) in a nutritional dissimulation test was higher (p = 0.015) than that of normal (1.0 +/- 0.7) or large eaters (1.5 +/- 0.09). This suggests that underreporting in obese small eaters might be due to specific nutritional concealment; because small eaters reported a low intake particularly in foods which are often perceived as unhealthy (fats, sugars, extra-prandial consumption), they probably reported what, in their opinion, they should have eaten, instead of what they did eat.