Estimation of food intake: effects of the unit of estimation.

While many studies have shown that individuals under-estimate caloric intake, few studies have examined how individuals estimate intake when using other units of measurement (e.g. cups, ounces). Forty-one women (21 obese, 20 normal weight) ate a test meal of Häagen-Dazs chocolate ice cream and were asked to estimate the amount they ate in both calories and cups. As expected, participants under-estimated intake when asked to estimate how much they ate in calories, but considerably over-estimated their intake when measured in cups. Thus, individuals can both under- and over-estimate how much of the same food they have eaten, depending on the unit they are asked to use for estimation. Obesity and eating disorders treatment programs should take into account the tendency to over-estimate volumetric portions as well as under-estimate caloric intake.