Effects of body weight regain on leptin levels: A systematic review and meta-analysis.

BACKGROUND: There are different changes observed before and after diet therapy, and also after weight regain. However, there is not sufficient information regarding weight regain and hormonal changes. PURPOSE: The purpose of this study was to review the connection between weight regain and leptin concentration levels. METHODS: MEDLINE, SCOPUS, Web of Science, and the Cochrane Library were searched for interventional articles published from January 1, 1980, to June 30, 2020. Randomized clinical trials with parallel or cross over design assessing leptin concentrations at the baseline and at the end of study were reviewed. Two independent reviewers extracted data related to study design, year of publication, country, age, gender, body mass index (BMI), duration of the following up period and mean ± SD of other intended variables. RESULTS: Four articles were included, published between 2004 and 2016. Three of them were conducted in the US and one of them in Netherland. Sample size of the studies ranged between 25 and 148 participants. The range of following up period was from13 to 48 weeks. The age range of participants was from 34 to 44 years. Our analysis shows that weight regain could reduce leptin levels, but this change is not statistically significant. CONCLUSION: This review suggests that weight regain may induce a non-significant reduction in leptin level. However, the limited number and great heterogeneity between the included studies may affect the presented results and there are still need to well-designed, large population studies to determine the relationship between weight regain and leptin levels.

Effect of extra virgin olive oil consumption on glycemic control: A systematic review and meta-analysis.

AIMS: Several health benefits are contributed to extra virgin olive oil (EVOO). The polyphenol fraction of EVOO may be responsible for its cardioprotective impacts. This systematic review and meta-analysis aimed to investigate the effect of EVOO intake on glycemic parameters. Electronic literature searched through 1 September 2020 across MEDLINE/PubMed, Web of Science, and SCOPUS databases to find all clinical trials that reported the effect of EVOO intake on glycemic parameters [FBS(fasting blood glucose), insulin, HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) and HbA1c (glycated hemoglobin A1c)] vs. control. DATA SYNTHESIS: We pooled standardized mean differences (SMD) and 95% confidence intervals (CIs) from randomized clinical trials (RCTs) using random-effects models. Heterogeneity was assessed by Cochran Q-statistic and quantified (I2). We found 13 related trials comprising a total of 633 subjects. In pooled analysis, EVOO intake had no effect on FBS (SMD: -0.07; 95% CI: -0.20, 0.07; I2 = 0.0%), insulin (SMD: -0.32; 95% CI: -0.70, 0.06; I2 = 38.0%), and HOMA-IR (SMD: -0.32; 95% CI: -0.75, 0.10; I2 = 51.0%). However, a decreasing trend was observed in these effects. Subgroup analysis based on age, health status, dose, and EVOO intake duration also did not significantly change results. CONCLUSION: Although EVOO seems a promising hypoglycemic effects, we did not find any significant evidence that EVOO consumption impacts glucose homeostasis. Furthermore, well-designed RCTs with longer durations are still needed to evaluate the EVOO's efficacy on glycemic parameters.

Effect of omega-3 fatty acids supplementation on cardio-metabolic and oxidative stress parameters in patients with chronic kidney disease: a systematic review and meta-analysis.

BACKGROUND: Omega-3 fatty acids (FAs) have been suggested as a beneficial supplement in chronic kidney disease (CKD) patients, but the results of randomized clinical trials (RCTs) are controversial. We conducted a systematic review and meta-analysis to evaluate all the RCTs about the impact of omega-3 FAs supplementation on cardiometabolic outcomes and oxidative stress parameters in patients with CKD. METHODS: We performed a systematic database search in PubMed/MEDLINE, EMBASE, Scopus, Web of Science, and Cochrane Central, up to May 2020. We included all placebo-controlled randomized trials that assessed the effect of omega-3 FAs supplementation on any cardiometabolic outcomes: blood pressure, total cholesterol (TC), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) or triglycerides (TG) and oxidative stress parameters. Data were pooled using DerSimonian-Laird's random-effects model. RESULTS: Finally, thirteen articles met the inclusion criteria for this review omega-3 FAs supplementation significantly decrease TC (SMD: -0.26; 95% CI: - 0.51, - 0.02; I2 = 52.7%), TG (SMD: -0.22; 95% CI: - 0.43, - 0.02; I2 = 36.0%) and Malondialdehyde (MDA) levels (SMD: -0.91; 95% CI: - 1.29, - 0.54; I2 = 00.0%) and also significantly increase superoxide dismutase (SOD) (SMD: 0.58; 95% CI: 0.27, 0.90; I2 = 00.0%) and Glutathione peroxidase (GPx) (SMD: 0.50; 95% CI: 0.14, 0.86; I2 = 00.0%) activities. However our results show that omega-3 FAs supplementation have no significant effects on HDL, LDL and blood pressure. Conclusion This systematic review and meta-analysis supports current evidence for the clinical benefit of omega-3 FAs intake to improve cardiometabolic parameters in CKD patients. However, well-designed RCTs still needed to provide a conclusive picture in this field.

Effect of ginger (Zingiber officinale) supplementation on oxidative stress parameters: A systematic review and meta-analysis.

A wide variety of antioxidant properties are attributed to ginger (Zingiber officinale) and several randomized controlled trials (RCTs) have investigated the effect of ginger intake on major oxidative stress (OS) parameters. We conducted a systematic review and meta-analysis to evaluate the effects of using ginger to improve OS levels. Medline, Scopus, ISI Web of Science, EMBASE, and the Cochrane Central Register of Controlled Trials were systematically searched up until March 2020 to gather RCTs that evaluated the impact of ginger intake on the levels and activity of OS parameters in adult subjects. Means and standard deviations for relevant OS variables were extracted and evaluated to assess the quality of the trials based on the Cochrane risk-of-bias tool for randomized trials. The gathered data were pooled and expressed as standardized mean difference (SMD) with 95% Confidence Intervals (95% CI). Twelve trials were included in this review. Ginger intake was shown to significantly increase glutathione peroxidase (GPx) activity (SMD: 1.64; 95% CI: 0.43, 2.85; I2  = 86.8%) and total antioxidant capacity (TAC) (SMD: 0.40; 95% CI: 0.06, 0.73; I2  = 42.8%) and significantly decrease malondialdehyde (MDA) levels (SMD: -0.69; 95% CI: -1.26, -0.12; I2  = 85.8%) compared to control groups. Ginger supplementation also non-significantly associated with an increase in CAT activity (SMD: 1.09; 95% CI: -0.07, 2.25; I2  = 87.6%). This systematic review and meta-analysis presents convincing evidence supporting the efficacy of ginger supplementation on improving OS levels. PRACTICAL IMPLICATIONS: In health sciences, OS, due to its pivotal role in the pathophysiology of several chronic diseases, is a subject with a long history. Recent research strives for a safe, ideal, and effective antioxidant. Ginger is herbal medicine, which has been widely used in traditional and complementary medicine. Proving the antioxidant effect and potential benefit of ginger has positive clinical implications for the application of this practical herb.

Effect of DASH diet on oxidative stress parameters: A systematic review and meta-analysis of randomized clinical trials.

BACKGROUND AND AIMS: Oxidative stress (OS) is one of the main risk factors for several chronic diseases. The Dietary Approaches to Stop Hypertension (DASH) contain many antioxidants and may contribute to managing OS. OBJECTIVE: To perform a systematic review and meta-analysis to examine the impacts of the DASH diet on OS parameters. METHODS: A comprehensive electronic search in MEDLINE, Scopus, EMBASE, and the Cochrane Central Register of Controlled Trials was performed through September 2020 to find related studies evaluating the impact of the DASH diet on OS parameters. Standardized mean differences were pooled using random-effects meta-analysis. RESULTS: Eight studies with a total of 317 subjects met our inclusion criteria. Four studies included in meta-analysis model with 200 participants (100 in treatment and 100 in control group). The DASH diet was associated with a statistically significant decrease in malondialdehyde (MDA) (SMD: -0.53; 95% CI: -0.89, -0.16; I2 = 42.1%), and a significant increase in glutathione (GSH) (SMD: 0.83; 95% CI: 0.36, 1.03; I2 = 42.1%). Meta-analysis found no statistically significant effect of DASH diet on nitric oxide (NO) (SMD: -1.40; 95% CI: -0.12, 1.93; I2 = 92.6%) or total antioxidant capacity (TAC) levels (SMD: 0.95; 95% CI: -0.10, 1.99; I2 = 87.6%). CONCLUSION: Our results demonstrated that a DASH diet could significantly increase GSH and decrease MDA levels. Furthermore, there is a trend to improve TAC, NO, and f2-isoprostanes by the adherence to the DASH diet. However, long-term, large sample size and well-designed randomized clinical trials are still needed to draw concrete conclusions about DASH diet's effects on OS parameters.