Halo or horn? The role of prior attitudes in shaping consumer responses to high-protein food labels

Front-of-pack nutrition claims can shape consumers' perceptions of food products by triggering inferences about their overall healthfulness. Among these claims, “high-protein” labels have rapidly expanded across food categories, yet their influence on consumers' nutritional judgments remains underexplored. The present study investigated whether a high-protein label induces a health halo effect and examined the role of product characteristics and individual differences in shaping these perceptions. In an online experiment ( N = 218), participants evaluated five food products presented either with or without a high-protein label. For each product, participants rated perceived calories, healthiness, sugar content, additives, level of processing, and purchase intention. Individual differences in drive for muscularity and attitudes toward protein products were also measured. Linear mixed-effects models revealed that the high-protein label did not produce a generalized positive halo effect: it did not significantly affect perceived healthiness, caloric content, sugar content, or purchase intention. However, products labeled as high protein were perceived as containing more additives and as being more industrially processed, consistent with a horn effect. The influence of the label on calorie and sugar estimations was moderated by the caloric content of the product, with effects emerging primarily for high-calorie products. Attitudes toward protein products moderated the label's effect across nutritional judgments, whereas drive for muscularity did not moderate labeling effects. These findings highlight the central role of individual predispositions in shaping responses to nutrition claims and suggest that high-protein labels may generate complex and sometimes contradictory perceptual biases, with implications for dietary behavior and public health.