Unaware of the amount consumed : Systematic error in estimating food- and drink intake

Background: Our current food environment promotes overconsumption due to the overrepresentation of foods that have a high calorie density and can be easily consumed. These food characteristics lead to limited oro-sensory exposure, which may lead to overconsumption due to insufficient perception of the amount consumed. Better perception of the amount eaten and thus a better ability to estimate intake may help control actual food intake through prolonged inter-meal interval and smaller meal sizes. Objective: The aim of this study was to determine whether food form, flavor and portion size influence the error in estimated intake (EiE). Method: Participants (n = 72) were recruited at a science festival where the study was also performed. The experiment had a 2 × 2 × 3 design with a reference condition. Experimental conditions differed in food form (liquid vs. solid stimuli), taste category (savory vs. sweet) and portion size (small, medium, large). Water was used as a reference condition. Results: Participants overestimated the amount consumed of all stimuli. The overestimation was ten times greater for solid compared to liquid products (104 ± 12 vs 12 ± 9% overestimation) and was more pronounced for sweet (75 ± 9%) than for savory products (41 ± 12%). There was a trend for larger EiE% of smaller portions. No differences were found among the differently flavored liquids including the water reference. Conclusion: People overestimate the amount they consume of solid and sweet products more than that of liquid and savory products. This overestimation may be due to overvaluation of the oro-sensory stimulation when visual cues and intake effort are controlled for or because of learned associations. However, the uncontrolled setting of the experiment should be taken into account when drawing conclusions. Future research may replicate the study in a more controlled setting and should determine whether the overestimation of sweet solid product intake also leads to lower intake at a subsequent meal