Effects of Antioxidant Supplementation on Metabolic Disorders in Obese Patients from Randomized Clinical Controls: A Meta-Analysis and Systematic Review

This systematic review and meta-analysis aim at elucidating the heterogeneity in beneficial effects of antioxidant supplementation in obese adults by exploring the differential effects of antioxidant supplementation on basic indicators of obesity, lipid metabolism, systemic antioxidant capacity, inflammatory biomarkers, and liver function.

The inclusion criteria specified randomized controlled trials with antioxidant intervention for adults (mean body mass index (BMI) > 30), from inception to Aug. 8, 2021, in the PubMed, Embase, The Cochrane Library, Web of Science, and Scopus databases. Meta-analysis and publication bias were performed using RevMan 5.4 software. Stata16 software was used to detect publication bias with Egger's and Begg's methods being mainly used. The data of basic indicators of obesity, lipid metabolism index, oxidative stress index, inflammatory biomarkers, and liver function index were collected to analyze the beneficial effects of antioxidant supplementation in obese patients.

A total of 30 studies were included in this study with a sample of 845 obese patients from the antioxidant supplementation group and 766 obese patients from the placebo control group. The meta-analysis showed that obese patients with antioxidant supplementation had lower BMI (mean difference (MD): - 0.44 [95%confidence interval (CI): - 0.84, -0.04], p = 0.03), waist circumference (MD : -0.78 [95%CI:-1.45, -0.11], p = 0.02), fasting blood glucose (FBG) level (standardized mean difference (SMD): - 4.92 [95%CI:-6.87, -2.98], p < 0.001) and homeostasis model assessment of insulin resistance (MD : -0.45 [95%CI:-0.61, -0.3], p < 0.001) when compared to the placebo group. Obese patients on antioxidant supplementation had lower levels of total cholesterol (SMD : -0.43 [95%CI:-0.84, -0.02], p = 0.04), triglycerides (SMD : -0.17 [95%CI:-0.31, -0.04], p = 0.01), low-density lipoprotein (SMD : -0.15 [95%CI:-0.29, -0.01], p = 0.03), malondialdehyde (SMD : -1.67 [95%CI:-2.69, -0.65], p = 0.001), and tumor necrosis factor-alpha (SMD : -0.29 [95%CI:-0.56, -0.02], p = 0.03), respectively, when compared to the placebo group. In addition, obese patients with antioxidant supplementation had higher levels of high-density lipoprotein (SMD : 0.25 [95%CI : 0.03, 0.46], p = 0.03) and superoxide dismutase (SMD : 1.09 [95%CI : 0.52, 1.65], p < 0.001) when compared to the placebo group. Antioxidant supplementation had no effects on other analyzed parameters including waist-hip ratio, leptin, fat mass, interleukin-6, C-reactive protein, alanine transaminase, and aspartate transaminase in obese patients.

The meta-analysis results indicated that antioxidant supplementation exerted potential beneficial effects in obese patients by regulating FBG, oxidative stress, and inflammation, whilst more high-quality studies are required to confirm these effects. The present study may provide important insights for the treatment of clinical obesity and obesity-associated complications.