Accuracy of food portion estimation by overweight and normal-weight subjects.

We found no definitive differences in the ability of overweight and normal-weight subjects to accurately estimate food portions. Therefore, our data do not support conclusions by others that overweight subjects are significantly less accurate than the normal-weight subjects in their estimates. However, our overweight sample included only 50% obese and was homogeneous as to education, income, and ethnicity. Nevertheless, we found serious errors in food portion estimation by all subjects. Moreover, our data support the findings of Rapp, which show inaccurate portion estimation even when subjects were actively involved in a diet counseling program. And, in general, our data support researchers who have concluded that inaccurate estimation of portion size is a major problem. If the results hold true across populations, the magnitude of errors could have a profound effect on the accuracy of our food composition data for therapeutic or monitoring purposes and requires creative modification of methods taught for monitoring and reporting food intake.