SummaryDietary energy density (DED) might be associated with the quality of the consumed diet. Therefore, this study was conducted to report the relationship between dietary energy density and diet quality index in Iranian youths. In this cross-sectional study we enrolled 410 female young adults in Isfahan-Iran who were selected according to the stratified random sampling method from among students of Isfahan University of Medical Sciences. A validated semi quantitative food frequency questionnaire was used to assess the usual dietary intakes. Dietary energy density was calculated as each individual's reported daily energy intake (kcal/d) into total weight of foods (excluding beverages) consumed (g/d). Diet quality was assessed by healthy eating index (HEI), nutrient adequacy ratio (NAR), and mean adequacy ratio (MAR). For calculating the NAR the ratio of daily individual intakes to standard recommended amounts for the subject's sex and age category was used. MAR was calculated as the sum of NARs divided by the number of nutrients ( n ϭ 10). Mean dietary energy density was 1.5 Ϯ 0.2 kcal/g and mean HEI was 57.5 Ϯ 16.0. Those in the highest quartile of DED had the lowest value for HEI, MAR, and NAR of zinc, calcium, vitamin C, vitamin B12 and vitamin B2 ( p Ͻ 0.05). Those in the highest quartile of DED had the highest prevalence of calcium, zinc, vitamin B2, vitamin B12, and vitamin C deficiency ( p Ͻ 0.05). Dietary energy density was inversely associated with the diet quality indices among Iranian young women adults. Key Words healthy eating index, dietary energy density, mean adequacy ratio, diet quality, nutrient adequacy ratio Total energy intake is one of the most important issues in the field of the relationship between dietary intake and the prevalence of the chronic diseases such as overweight and obesity ( 1 ). However, recently the amount of energy in a given weight of food named as dietary energy density is considered as a determinant of non-communicable diseases ( 2-6 ). There are some cross-sectional and prospective reports regarding the association between dietary energy density and obesity, metabolic syndrome and type 2 diabetes ( 7-12 ). A clinical trial also confirmed that reduced dietary energy density had resulted in significant weight loss ( 13 ). Preliminary findings suggest that consuming a diet lower in ED may aid with weight loss maintenance ( 14 ).Energy density of the diets could also be associated with the healthy or unhealthy characteristic of the diets. Energy-dense diets have been reported to contain higher amounts of fat, refined grains and added sugars, but lower amounts of fruits and vegetables, wholegrains and dietary fiber. High dietary energy density is associated with unhealthy food choices ( 15 ). The main characteristic of energy-dense diets is higher amounts of saturated and trans fats and a higher glycemic load ( 15 ). According to a previous report, consumption of a low-energy-dense diet had been associated with higher intakes of micronutrient-rich foods, lower intakes of...