The association between dietary sodium intake and obesity in adults by sodium intake assessment methods: a review of systematic reviews and re-meta-analysis

BACKGROUND/OBJECTIVES: The scientific evidence of a sodium-obesity association is limited by sodium intake assessments. Our specific aim is to synthesize the association between dietary sodium intake and obesity across the sodium intake assessments as evidenced by systematic reviews in adults. SUBJECTS/METHODS: A systematic search identified systematic reviews comparing the association of dietary sodium intakes with obesity-related outcomes such as body mass index (BMI), body weight, waist circumference, and risk of (abdominal) obesity. We searched PubMed on October 24, 2022. To assess the Risk of Bias in Systematic Reviews (ROBIS), we employed the ROBIS tool. RESULTS: This review included 3 systematic reviews, consisting of 39 unique observational studies (35 cross-sectional studies and 4 longitudinal studies) and 15 randomized controlled trials (RCTs). We found consistently positive associations between dietary sodium intake and obesity-related outcomes in cross-sectional studies. Studies that used 24-h urine collection indicated a greater BMI for those with higher sodium intake (mean difference = 2.27 kg/m(2); 95% confidence interval [CI], 1.59–2.51; P < 0.001; I(2) = 77%) compared to studies that used spot urine (mean difference = 1.34 kg/m(2); 95% CI, 1.13–1.55; P < 0.001; I(2) = 95%) and dietary methods (mean difference = 0.85 kg/m(2); 95% CI, 0.1–1.51; P < 0.05; I(2) = 95%). CONCLUSIONS: Quantitative synthesis of the systematic reviews has shown that cross-sectional associations between dietary sodium intake and obesity outcomes were substantially different across the sodium intake assessments. We need more high-quality prospective cohort studies and RCTs using 24-h urine collection to examine the causal effects of sodium intake on obesity.