Background Orthorexia nervosa (ON) is characterized by an excessive, obsessive concern with healthy eating generating psychological complications and even malnutrition at a caloric and protein level. Current evidence suggests that people with greater food knowledge are the most likely to be affected, placing nutrition students as a populational risk group. Since there are no nationwide studies dealing with orthorexia nervosa in this risk group, the present pilot study intends to identify risk factors for orthorexia nervosa in a sample of Nutrition and Dietetics students in Chile. Method A descriptive cross-sectional pilot study was done on 90 Nutrition and Dietetics students from a Chilean university, representing 70% of its population. The ORTHO-11-ES instrument was applied to determine ON risk, along with consulting about attitudinal, physical-clinical and social variables. Statistical tests were performed in GraphPad PRISM 8.0®, applying probability ratios and personal correlation, between the sociodemographic variables and the risk of orthorexia nervosa. This study was approved by the university Ethics Committee based on the Helsinki Declaration. Results 23.3% of the studied population was at risk of suffering ON. Associated variables were being in the second year of their major (OR 2.22), coming from a charter school (OR 3.00) and cohabitation being limited to ≤ 1 person (OR 2.47). Particularly, declared physical activity limits are associated to the risk of suffering ON (Sedentary OR 2.42, Heavy OR 3.53), as well as time spent on the social network Instagram (< 1 h OR 2.77, > 3 h OR 1.80). Conclusions There is an ON risk prevalence of 23.3% in the present pilot sample under study, indicating that years of study, cohabitation, secondary educational establishment, physical activity and Instagram use constitute associated factors for the studied condition. Some results vary from international evidence, describing a dual nature in the variables for Instagram time and declared physical activity for ON risk. This study needs replication in more representative samples and longitudinal character with control groups which can confirm the studied elements as ON risk factors. Plain English summary Orthorexia nervosa (ON) is an expression created to indicate a possible new eating disorder characterized by excessive and obsessive preoccupation with healthy eating. Some of its most distinctive traits include marked anxiety over food, exaggerated fear over the appearance of some diseases and shame about physical appearance. This ultimately impacts food choice, planning, acquisition, preparation and consumption, creating psychological complications along with some associated with malnutrition. Considering that Nutrition students are an at-risk group, the present pilot study evaluated its prevalence and associated factors in a specific sample in Chile. Conditions associated with the risk of orthorexia nervosa identified in the present study include: number of hours spent using Instagram, limited cohabitation, extreme physical activity, and number of years in the major. These results should be taken cautiously, with their association confirmed in follow-up studies.