Meal Size, Not Body Size, Explains Calorie Underestimation

While most people underestimate the calories they consume during a meal or during the day, calorie underestimate is especially extreme among overweight individuals. This has often been attributed to motivational biases – denial and impression management – and has been clinically treated as such. In a food court field study, lunchtime diners estimated the number of calories in the fast‐food meal they had just consumed. In a second laboratory study, 40 adults estimated the number of calories of 15 different meals. The field study involved 105 normal weight and overweight/obese lunchtime diners (Body Mass Index of 17.2–33.5 kg/m 2 ). The laboratory study involved 40 adults (Body Mass Index of 16.1–32.3 kg/m 2 ). Participants were asked to estimate the calories in a meal they had just ordered and eaten (field study) or in 15 meals they were shown (lab study). Their estimates were compared with actual calorie levels. While the number of calories of larger meals was strongly underestimated (by −38.0% in Study 1 and by −22.6% in Study 2), the number of calories of smaller meals was more accurately estimated (by −2.9% in Study 1 and by +3.0% in Study 2). After controlling for meal size, the estimations of normal weight and overweight participants were similar, in both Study 1 (t = −1.2, p = 25) and Study 2 (F (1,594) =.18, p = .89). The larger underestimation of calories by overweight individuals is simply an unintended consequence of their tendency to consume larger meals.