The aim of the present study was to investigate the possible associations between dietary energy density (ED) and the metabolic syndrome (MetS) in patients with type 2 diabetes. In the present case–control study, the dietary ED of 125 patients with type 2 diabetes (seventy-eight with (cases) the MetS and forty-seven without (controls) the MetS; mean age 62·0 (sd 9·4) years, mean diabetes duration 12·5 (sd 8·4) years and mean glycated Hb 7·2 (sd 1·3) %) was assessed by weighed diet records. The MetS was defined according to the 2009 Joint Interim Statement and ED by the amount of energy (kJ) in a given weight of food. Data are expressed as means (standard deviations) or medians (interquartile ranges). Patients with the MetS reported lower intakes of total energy and fibre, and a higher total food amount than the controls; the total ED did not differ, but the cases had a higher ED at lunch (mean 6·3 (sd 1·3) v. 5·9 (sd 0·8) kJ/g; P= 0·017). In this meal, patients with the MetS had lower intakes of beans (median 0·7 (interquartile range 0·4–1·1) v. 1·1 (interquartile range 0·6–1·6) g/kg; P= 0·020), vegetables (median 1·2 (interquartile range 0·6–1·7) v. 1·4 (interquartile range 1·0–2·0) g/kg; P= 0·046) and total meat (median 1·3 (interquartile range 1·0–1·6) v. 1·4 (interquartile range 1·2–1·8) g/kg; P= 0·034) than patients without the MetS. The associations between lunch ED (kJ/g) and food groups (g/kg) were confirmed for vegetables (r − 0·584; P< 0·001), fruits (r − 0·233; P= 0·070), beans (r − 0·189; P= 0·037) and oils (r 0·323; P< 0·001). In a multivariate logistic regression model, a high lunch ED was associated with the MetS (OR 6·89, 95 % CI 1·35, 35·15; P =0·020) after adjusting for confounders. In conclusion, a high ED at lunch increased the odds of the presence of the MetS in patients with type 2 diabetes. Beans and vegetables may be the major contributors to this association and their consumption might be considered to decrease ED.