Association of nocturnal lifestyle with overweight and obesity: a cross-sectional study based on SHOOW (Shanghai Overweight/Obesity and Wellness Study) cohort

This study aims to examine the associations between nocturnal lifestyle and overweight/obesity, especially central obesity. While most previous studies have examined individual nocturnal lifestyle factors separately, this study simultaneously evaluates three nocturnal lifestyle behaviors (weekly midnight snack frequency, bedtime, and sleep duration) in a clinical sample of overweight and obese adults, with a specific focus on central obesity indicators. The study was based on clinical data of 1295 overweight and obese patients collected from a weight management outpatient clinic. We analyzed the associations between weekly midnight snack frequency, bedtime, sleep duration and obesity-related indicators. Female patients accounted for 69.19% (896 cases) and male patients accounted for 30.81% (399 cases). Young and middle-aged adults (18–49 years old) constituted the largest proportion, reaching 91.51%. In terms of weekly midnight snack frequency, 58.92% of patients (763 cases) did not consume midnight snacks, 29.96% (388 cases) consumed midnight snacks 1–3 times per week, and 11.12% (144 cases) consumed midnight snacks 4–7 times per week. The largest group of patients (786 cases, 60.70%) went to bed between 22:00 and 24:00, while 409 patients (31.58%) fell asleep between 24:00 and 2:00. Most patients (1111 cases, 85.79%) had a nocturnal sleep duration of 4–8 h. Univariate linear regression analysis showed that weekly midnight snack frequency (4–7 times/week) was significantly positively associated with body mass index ( BMI , P = 0.017) and waist circumference ( WC , P = 0.003); weekly midnight snack frequency (1–3 times/week) was significantly positively associated with waist-to-hip ratio ( WHR , P = 0.009). Compared with the 22:00–24:00 bedtime group, the after 2:00 group was significantly associated with all obesity indicators. The 24:00–2:00 group was significantly associated with all obesity indicators except body fat percentage ( BFP ). Concerning sleep duration, compared with the 4–8 h group, the > 8 h group was significantly associated with higher BMI ( P = 0.002), neck circumference ( NC , P = 0.008), WC ( P = 0.003), WHR ( P = 0.046) and upper arm circumference ( UAC , P = 0.008). Multivariate linear regression analysis further confirmed that WC and WHR was jointly associated with weekly midnight snack frequency, bedtime and sleep duration. Nocturnal lifestyle was mainly associated with central obesity indicators, and adjustment of nocturnal lifestyle habits may be a consideration for central obesity prevention efforts.