Measuring ‘expected satiety’ in a range of common foods using a method of constant stimuli

Humans have expectations about the satiety that is likely to develop after consuming particular foods. These expectations are potentially important, because they may influence decisions about meal size. Despite this, very little is known about the basis on which satiety expectations are formulated. This work introduces a methodology (based on a method of constant stimuli) that quantifies differences in expectations across foods. In Experiment 1 (N = 52) and Experiment 2 (N = 76) we compared expectations across 4 and 18 common foods, respectively. We discovered that a considerable mismatch occurs between satiety expectations and the energy content of foods (e.g., 200 kcal of pasta and 894 kcal of cashew nuts are expected to deliver equal satiety). This difference may reflect physical or macronutrient characteristics of these foods – energy-dense and high-fat foods have significantly lower ‘ratios of expected satiety.’ We also found a highly significant relationship between food familiarity and expected satiety (r = 0.86, p < 0.001), suggesting that expected-satiety judgements are learned. Across experiments, we were able to confirm both the reliability and robustness of our empirical approach. Future use of this methodology is discussed, both in relation to our understanding of portion-size decisions and its application more generally.