Undernutrition among hospitalized patients is highly prevalent. In contrast, the obesity pandemic is increasing in prevalence among all, including cardiology patients. The dietary challenge during hospitalization is to provide a healthy diet that stimulates the appetite and is suitable for both patients at risk of undernutrition and of cardiovascular events. The aim of the present study was to compare energy and macronutrient intake between a conventional hospital menu (Fixed) with a concept providing free serving hours and ad libitum intake à la carte (Free) among cardiology patients. The comparison was done between concepts for all lean (BMI < 25 kg/m2) and overweight and obese (BMI ≥ 25 kg/m2) patients and subgroups. Food intake was registered during a 3-week period on Fixed for forty-eight randomly selected patients and later by two similar time periods on Free1 for twenty-eight and Free2 for thirty-seven other patients. Free compared with Fixed increased the energy intake – but not above requirement – among the obese only (P < 0·001; Free v. Fixed). This was explained by an increase in the relative fat intake of 50 % (P < 0·001) and 37 % (P < 0·001) for Free1 and Free2 respectively. During Free1, the relative fat intake correlated positively with BMI (r 0·6; P < 0·01), and the relative carbohydrate intake negatively with BMI (r − 0·7; P < 0·01); the same pattern was seen during Free2, although insignificant. We conclude that the introduction of an ad libitum à la carte kitchen (Free) to cardiology patients slightly increases the average nutritional intake, but contains a potential health hazard for overweight cardiovascular patients, due to the selection of high-fat dishes and decreased carbohydrate intake. This emphasises the need for improvement in fat sources and in dietary advice when an ad libitum concept is applied during hospitalization.