Social jetlag and obesity: A systematic review and meta-analysis.

Social jetlag, the weekly variation in sleep timing, is proposed to contribute to increased obesity risk, potentially because of the misalignment of behavioral cycles relative to the endogenous circadian timing system. This systematic review and meta-analysis aim to determine the association between social jetlag and adiposity-related measures using observational studies. We reviewed 477 references, of which 43 studies met inclusion criteria with a total sample size of 231,648. There was a positive association between social jetlag and body mass index (correlation coefficient [r]: 0.12; 95%CI, 0.07, 0.17; P < 0.001; I 2  = 94.99%), fat mass (r: 0.10; 95%CI, 0.05, 0.15; P < 0.001; I 2  = 0.00%), fat mass index (fat mass divided by height in meter squared, β: 0.14 kg/m 2 ; 95%CI, 0.05, 0.23; P < 0.001; I 2  = 56.50%), percent of body fat (r: 0.37; 95%CI, 0.33, 0.41; P < 0.001; I 2  = 96.17%), waist circumference (r: 0.15; 95%CI, 0.06, 0.24; P = 0.001; I 2  = 90.83%), and the risk of having overweight/obesity (odds ratio: 1.20; 95%CI, 1.02, 1.140; P = 0.039; I 2  = 98.25%). Social jetlag is positively and consistently associated with multiple obesity-related anthropometric measures. Further studies are needed to test causality, underlying mechanisms, and whether obesity interventions based on increasing regularity of the sleep/wake cycle can aid in the battle against the obesity pandemic.