Background Malnutrition affects between 25 and 40% of all hospitalized patients, the majority of whom receive their main nutritional intake from the food provided by the hospital catering system. There is currently very little published information concerning the nutritional impact on patients of different methods of catering service.Objective In the current study the effects of two catering service systems, plated and bulk service, on food and nutrient intake of hospital patients were compared.Methods One-hundred and eight patient meals were surveyed, 51 on the plated meal and 57 on the bulk meal services. Patients were either on a general medical or an orthopaedic ward. Weighed food intake data were collected by weighing food served and comparing it to the weight of food left on the plate. Equal numbers of lunch and supper dishes were weighed. Also, a number of weekend surveys were carried out to take into account variation in service at weekends.Results Food wastage was greater with the plated system. Comparing the amount of energy and nutrients consumed by patients according to meal system: energy intakes were significantly lower with the plated system (414 ± 23 kcal vs. 319 ± 22 kcal, P < 0.004). Protein, fat and carbohydrate intakes were also significantly lower. The main reason for the observed differences was the higher total food intake of the main course of the bulk service meals. Energy intake from the main course was significantly higher among patients receiving bulk service meals (227 ± 10 kcal vs. 165 ± 14 kcal, P < 0.006).Conclusion Catering service systems can have a major impact on the nutritional intake of hospitalized patients.