Undereating and underrecording of habitual food intake in obese men: selective underreporting of fat intake

Background: Underreporting of food intake is common in obese subjects. Objective: One aim of this study was to assess to what extent underreportin g by obese men is explained by underrecording (failure to record in a food diary everything that is consumed) or undereating. Another aim of the study was to find out whether there was an indication for selective underreporti ng. Design: Subjects were 30 obese men with a mean (+/-SD) body mass index (in kg/m(2)) of 34 +/- 4. Total food intake uas measured over 1 wk. Energy expe nditure (EE) was measured with the doubly labeled water method, and water l oss was estimated with deuterium-labeled water. Energy balance was checked for by measuring body weight at the start and end of the food-recording wee k and 1 wk after the recording week. Results: Mean energy intake and EE were 10.4 +/- 2.5 and 16.7 +/- 2.4 MJ/d, respectively; underreporting was 37 +/- 16%. The mean body mass loss of 1. 0 +/- 1.3 kg over the recording week was significantly different (P < 0.05) from the change in body mass over the nonrecording week, and indicated 26% undereating. Water intake (reported + metabolic water) and water loss were significantly different from each other and indicated 12% underrecording. The reported percentage of energy from fat was a function of the level of u nderreporting: percentage of energy from fat = 46 - 0.2 x percentage of und erreporting (r(2) = 0.28, P = 0.003). Conclusions: Total underreporting by the obese men was explained by underre cording and undereating. The obese men selectively underreported fat intake .