The association of dietary energy density and the risk of obesity, type 2 diabetes and metabolic syndrome: A systematic review and meta-analysis of observational studies.

OBJECTIVES There is a growing body of evidence linking dietary energy density (DED) with metabolic disorders like obesity, type 2 diabetes (T2D) and metabolic syndrome (MetS). However, according to our knowledge, there has been no systematic review and mate-analysis on T2D and MetS with DED. Therefore, this study aimed to investigate the association between DED with the risk of obesity, T2D and MetS in a systematic review and meta-analysis of observational studies. METHODS We searched all published studies according to the defined keywords up to march 2020 in the PubMed/Medline and Scopus databases. We excluded those that did not calculate DED for total intake, no observed association between obesity, T2D, MetS as the primary or one of the outcomes with DED, no reported odds ratio (OR), relative risk (RR) or hazard ratio (HR) estimates with 95% confidence intervals (CIs), studies in children under 2 years old, patients with cancer and pregnant women. RESULTS From 2282, after deleting the duplicates and irrelevant studies, we entered 58 articles ( 47 systematic reviews and 11 meta-analyse). We indicated an increased risk of T2D in relation to DED (OR: 1.25, 95% CI: 1.18-1.33, P < .001). But studies reviewed were inconsistent. All studies which examined the relationship between DED and MetS showed a positive relationship with an increased significant risk (OR: 1.59, 95% CI: 1.22-2.07, P < .001). Most articles reported a direct association between DED and obesity but the relationship between DED and risk of obesity was not significant (OR: 1.04, 95% CI: 0.92-1.17, P = .543). CONCLUSION In this systematic review and meta-analysis of observational studies, we found that the DED increased the risk of T2D and MetS but was not significant with the risk of obesity.