Impact of walnut consumption on glycemic control and anthropometric indices: a systematic review and meta-analysis of randomized controlled trials

Objectives

Previous studies have led to conflicting results regarding the effect of walnut consumption on glycemic control, and anthropometric indices. This study aimed to evaluate the efficacy of walnut consumption on serum levels of fasting blood sugar (FBS), fasting insulin, hemoglobin A1C (HbA1c), homeostasis model assessment of insulin resistance (HOMA-IR), weight and body mass index (BMI) through a systematic review and meta-analysis of randomized controlled trials (RCTs).

Methods

PubMed, Scopus, Web of Science, and the Cochrane databases were searched up to February 2023. Weighted mean difference (WMD) was analyzed using random effects models to assess the overall effect.

Results

A total of thirty-two RCTs were included in the systematic review and meta-analysis. Walnut supplementation was found to significantly reduce HOMA-IR (WMD = -0.29; 95% CI: -0.57, -0.01, P = 0.04), and body weight (WMD = -0.14 kg; 95% CI: -0.24, -0.04; P = 0.008). However, the meta-analysis showed that walnut supplementation did not have a significant effect on FBS (WMD = 0.62 mg/dL; 95% CI: -0.66, 1.91; P = 0.34), insulin levels (WMD = 1.27 mIU/ml; 95% CI: -0.59, 3.14; P = 0.18), HbA1C (WMD = 0.00%; 95% CI: -0.09, 0.10; P = 0.95), and BMI (WMD = -0.10 kg/m2; 95% CI: -0.40, 0.20; P = 0.50).

Conclusion

In conclusion, this study found a significant reduction in HOMA-IR levels and body weight with walnut supplementation, while other glycemic markers, and obesity-related indices did not change significantly. Future well-designed trials are needed to confirm these results.

Ultra-processed food consumption and adult obesity risk: a systematic review and dose-response meta-analysis

We performed this systematic review and meta-analysis to evaluate observational studies assessing the association between ultra-processed food (UPF) consumption and the risk of overweight, obesity, and abdominal obesity in the general population. We searched the databases PubMed/MEDLINE, Scopus, Embase, and ISI Web of Science from inception until December 2020. Data were extracted from 12 studies (nine cross-sectional and three cohort studies). Odds ratio (OR) were pooled using a random-effects model. UPF consumption was associated with an increased risk of obesity (OR = 1.55; 95% CI: 1.36, 1.77; I² = 55%), overweight (OR = 1.36; 95% CI: 1.14, 1.63; I² = 73%), and abdominal obesity (OR = 1.41; 95% CI: 1.18, 1.68; I² = 62%). Furthermore, every 10% increase of UPF consumption in daily calorie intake was associated with a 7%, a 6%, and a 5% higher risk of overweight, obesity, and abdominal obesity, respectively. Dose-response meta-analysis of cross-sectional studies showed a positive linear association between UPF consumption and abdominal obesity. There was also a positive linear association between UPF consumption and risk of overweight/obesity in the analysis of cross-sectional studies and a positive monotonic association in the analysis of cohort studies. Our study suggests that UPF consumption is associated with an increased risk of excess weight or abdominal obesity.

Association of serum and follicular fluid leptin and in vitro Fertilization/ ICSI outcome: A systematic review and meta-analysis

There are conflicting reports regarding circulating leptin and its relationship between pregnancy outcomes in infertile women undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). We performed a systematic review and meta-analysis to assess the association between serum or follicular fluid (FF) leptin concentrations reported for infertile women and their IVF outcome. A systematic search was undertaken in available databases (PubMed, Scopus, Web of Science, The Cochrane Library and Embase) to find studies published up to Aug 2020 and the standardized mean difference with 95 % confidence interval was taken from 14 eligible studies. Both graphical (funnel plots) and test methods (Egger's regression test and the Begg) assessed the presence of publication bias. Subgroup analysis was used to investigate the source of heterogeneity. Pooled effect sizes based on the eligible papers indicated that of there is no statistically significant correlation between leptin levels in follicular fluid and serum on the day of ovum pick-up (OPU) and day of HCG (human chorionic gonadotrophin) administration in pregnant and non-pregnant women who underwent IVF/ICSI cycles. However, combination of leptin in serum and/or FF with other parameters may be a useful marker to predict IVF outcome.