Restrict for Thinness or for Health? Liking but Not Approach Bias Differentiates Anorexia from Orthorexia Nervosa in Responses to High-Caloric Healthy vs. High-Caloric Unhealthy Foods

Objective: The (pathological) fixation on healthy eating in individuals with orthorexia (OR) shares features with anorexia nervosa (AN), raising debate over whether OR constitutes a distinct disorder. A key distinction may lie in preference for and approach behaviour toward foods differing in calorie content and healthiness. We expected reduced liking and a stronger approach bias in AN and OR compared with controls; in AN specifically for high-caloric foods and in OR specifically for unhealthy foods.Methods: Individuals with self-reported AN diagnosis (N = 35), OR (high scores on the Düsseldorf Orthorexia Scale but no AN; N = 40), and controls (no eating disorder history, N = 101) completed liking ratings and an Approach-Avoidance Task with food stimuli varying in calorie content (high vs. low) and, for high-calorie items, healthiness (healthy vs. unhealthy). Results: Compared to controls, AN reported lower liking for all high-caloric foods, while OR reported lower liking only for high-caloric, unhealthy foods. Accordingly, OR also liked high-caloric healthy foods more than AN. AN showed weaker approach bias than controls (mainly driven by high-caloric unhealthy foods). OR descriptively lay between both other groups, with no significant differences in approach bias to either.Conclusion: Explicit liking ratings distinguished AN from OR aligning with their respective motivation to reduce high caloric versus unhealthy food intake. Reduced approach bias was specific to AN, possibly reflecting rapid engagement of approach-avoidance responses to easy-to-categorize high-caloric unhealthy foods. Contrary, health-focused processing in OR may require slower deliberations that are not captured by Approach-Avoidance Tasks.