Greater affluence and the accompanying shift in standards of living have led to obesity becoming a global epidemic affecting over two billion people today. Oxidative stress is one of the products of obesity, brought about by factors that include the oxidation of fatty acids and over-consumption of oxygen.
With oxidative stress a major component of obesity, there have been numerous studies on the impact of antioxidant supplementation on obesity and its indicators. Researchers at Hengyang Maternal and Child Health Hospital, the University of South China and Youjiang Medical University therefore sought to determine “the heterogeneity in beneficial effects of antioxidant supplementation in obese adults”.
Through a systematic review and meta-analysis of 30 randomized, controlled trials (RCTs), they explored the differential effects of antioxidant supplementation on “basic indicators of obesity, lipid metabolism, systemic antioxidant capacity, inflammatory biomarkers, and liver function”.
Antioxidants — a viable anti-obesity measure?
The studies included in the review had a total of 845 obese patients who had been given antioxidant supplementation and 766 obese patients in placebo control groups.
Overall, the meta-analysis showed that the study subjects who had received antioxidant supplementation were found to have lower BMI, waist circumference and fasting blood glucose (FBG) levels, as well as reduced insulin resistance, when compared to those in the placebo groups.
Obese patients on antioxidant supplementation also had lower levels of metabolic disorder markers, including total cholesterol, triglycerides and low-density lipoprotein (LDL), compared to those in the placebo groups.
Additionally, the subjects in the supplemented groups were found to have higher levels of high-density lipoprotein (HDL) and superoxide dismutase than those in the placebo groups. However, antioxidant supplementation appeared to have had no effects on other factors in the obese study subjects, such as leptin, fat mass and waist-to-hip ratio.
With regards to the mechanism by which antioxidants work to combat metabolic disorders in obese individuals, the researchers highlighted the distinction between the different chemical structures used to classify them into two gross divisions: hydrophilic (water-soluble) and hydrophobic (fat-soluble).
The former reacts with reactive oxygen species (ROS) in cells or bodily fluids, while the latter tends to protect cell membranes from ROS-mediated lipid peroxidation — a process whereby oxidants like free radicals attack lipids such as polyunsaturated fatty acids (PUFAs) and cause cell membrane damage.
While these results were consistent with previous findings, the researchers also acknowledged that there may have been publication bias in the included studies. As such, they recommended “more high-quality studies” to further confirm the impact of antioxidants on regulating lipid metabolism disorder.
Furthermore, they had only analysed and reviewed a small number of studies, all of which were in English and most of which involved heterogeneous results in cumulative analyses. On the other hand, the antioxidant types included in the review were varied, making it unclear which antioxidant was the most effective against metabolic disorders in obesity.
The researchers added: “Our subgroup analysis showed that different types of antioxidants had differential effects on metabolic disorders, while the specific roles of water- and fat-soluble antioxidants in obese patients may still require further studies.”
Still, they noted that the results of their meta-analysis“indicated that antioxidant supplementation exerted potential beneficial effects in obese patients by regulating FBG, oxidative stress and inflammation, and could provide vital insights into treating clinical obesity and its related complications.
Source: Oxidative Medicine and Cellular Longevity
“Effects of Antioxidant Supplementation on Metabolic Disorders in Obese Patients from Randomized Clinical Controls: A Meta-Analysis and Systematic Review”
Authors: Jinyuan Wang, et al.