Non-linear estimates of nutritional properties, driven by health biases, lead to systematic errors in caloric food choice

Maintaining a daily caloric deficit while dieting underlies most successful weight lossprograms. Accurate estimation of caloric content is central to effective dietary regulation, yetmost everyday food choices rely on subjective judgments rather than labeled nutritionalinformation. We investigated whether these judgments are systematically biased and how suchbiases influence caloric decision-making. In Experiment 1, online participants estimated thecaloric and macronutrient content of 68 photographed foods. Across nutrients, subjectiveestimates were better characterized by a logarithmic than a linear function of objectivenutritional values, consistent with previous results (Carrington et al., 2024), suggesting Weber–Fechner–like magnitude compression. Additionally, the degree of non-linearity scaled with eachnutrient’s association with perceived healthfulness; caloric estimates were most strongly(negatively) correlated with healthfulness judgments.In Experiment 2, participants completed a forced-choice task selecting the higher-calorieitem from pairs of foods that differed by ~200 kcal or ~100 kcal. Choice accuracy declined asthe average caloric magnitude of food pairs increased, consistent with the magnitudecompression model. Critically, errors were disproportionately driven by “health conflict” trials, inwhich perceived healthfulness opposed actual caloric differences. Participants who relied moreheavily on perceived healthfulness were significantly less accurate overall.Together, these findings demonstrate that caloric judgments are shaped by bothpsychophysical compression and healthfulness heuristics. When caloric discrimination becomesdifficult, particularly among calorie-dense foods, individuals substitute health-based impressionsfor objective magnitude computations, leading to systematic and predictable errors. Such biasesmay contribute to everyday misestimation of energy intake with cumulative consequences forweight regulation.