The Effects of Purslane Consumption on Obesity Indices: A GRADE-Assessed Systematic Review and Meta-Analysis of Randomized Controlled Trials

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Introduction
Obesity is a preventable threat to human health, characterized by excessive fat accumulation in the adipose tissue, caused by an unequal balance between energy expenditure and intake [1,2].According to the latest report published by the World Health Organization (WHO) in 2016, 39% of the global adult population (≥18 years) were overweight, while 13% were classifed as obese [3].Meanwhile, the obesity epidemic is rapidly spreading across the Asia-Pacifc region.Te prevalence of obesity in West Asia and East Asia reached 11.9% and 24.5%, respectively [4].Specifcally, obesity and overweight are serious public health issues in Iran, afecting a large proportion of the adult population.Recent estimates suggest that 22.7% of the adults are obese and 59.3% are overweight [5].Various comorbidities are associated with obesity, such as hyperlipidemia, metabolic syndrome (MetS), coronary heart disease, cancer, hypertension, mental disorders, and diabetes [6].Infammatory states induced by excess body fat may contribute to obesity's association with these diseases.Despite some attempts to prevent and control obesity and its complications, these strategies are challenging to implement correctly and have had limited success over time [7].Currently, lifestyle modifcation and pharmacological or herbal interventions [8][9][10] are being used for treating obesity, which focuses on reducing appetite and increasing the basal metabolic rate [11,12].Herbal supplements have become increasingly popular due to their fewer adverse efects and lower cost compared to manufactured medications [13,14].
Purslane, a member of the Portulacaceae family, is one of the most widely used medicinal plants [15].It has been traditionally used to treat many diseases due to its antiinfammatory and antioxidant properties [16] and its active biologic compounds that are benefcial to human health [17].Purslane's most active compounds include omega-3, tocopherol, carotene, amino acids, thiamine, ascorbic acid, niacin, and phenolic compounds such as quercetin, kaempferol, cafeic acid, ferulic acid, and p-coumaric acid [18].Purslane has the highest concentration of omega-3 fatty acids, particularly alpha-linolenic acid, when compared to other leafy green vegetables [19].Tis makes it an elixir or panacea used for various therapeutic purposes [20].Several studies have reported that purslane seeds or purslane extract may have antiobesity properties [21][22][23].
Te compounds niacin and thiamine present in purslane may be responsible for its efectiveness in weight reduction.Tis is because they act as coenzymes in the conversion of carbohydrates, fats, and proteins into usable energy [21].Te antiobesity properties of purslane may also be exerted by its efect on insulin [21].However, the precise efects of purslane on anthropometric indices remain unclear.To our knowledge, there is no systematic review or meta-analysis of randomized controlled trials (RCTs) that evaluated purslane's efect on obesity indices.Terefore, this study aimed to determine whether purslane supplementation afected body weight (BW), body mass index (BMI), and waist circumference (WC) among adults.

Methods
Tis meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (Supplementary Table 1) [24].Te protocol of the current study has been registered in the International Prospective Register of Systematic Reviews (PROSPERO) system under the registration number CRD42023426343.Te present systematic review and metaanalysis protocol has been approved by the Ethics Committee of Isfahan University of Medical Sciences (approval number: IR.MUI.RESEARCH.REC.1402.108and grant number: 140275).

Search Strategy.
To identify relevant papers from inception until May 2023, various electronic databases including Web of Science, EMBASE, PubMed, Scopus, and Cochrane Library databases were searched.Te following MESH and non-MESH words were used: ("Portulaca" OR "Purslane" OR "Portulaca oleracea") AND ("waist circumference" OR "weight loss" OR "BMI" OR "obesity" OR "Overweight" OR "weight" OR "Body Mass Index" OR "adipose tissue" OR "fat mass" OR "WC" OR "adiposity" OR "WHR" OR "waist-to-hip ratio").Tere were no language restrictions.Other relevant publications were also identifed by reviewing the reference lists of the included studies.In order to obtain the full text for those articles that met inclusion criteria but were not available in full text, their authors were contacted via email.

Study Selection.
Te inclusion criteria for the studies were as follows: (1) crossover or parallel-design controlled clinical trials, (2) involving individuals aged 18 years and older, (3) reporting at least one of the following variables: BW, BMI, and WC in both treatment and placebo groups before and after the intervention, and (4) reporting mean and standard deviation (SD) values of one of the following measures: BW, BMI, and WC.For datasets containing multiple publications, only the complete study was included.However, several studies were excluded because they did not meet the inclusion criteria.Specifcally, studies were excluded if they (1) did not have a placebo or control group, (2) did not have adequate outcomes data in either intervention or control groups, (3) were patents or dissertations, (4) involved children, pregnant women, or animals, and (5) evaluated the combined efect of purslane with other interventions such as obesity drugs (antidepressant, corticosteroid, and so on).

Data Extraction.
Two investigators (SH and MV) independently extracted data from eligible studies, and the principal investigator (MB) determined whether there was disagreement to reach an agreement.Te following information was collected: the frst author's name, the study design, the publication year, the duration of the trial, the study location, the dose of purslane, the intervention form, the health status of the participants, their mean ages, their sexes, the sample size for the control and intervention groups, and the mean changes and SD of anthropometric measures for the control and intervention groups.

Study
Quality and Certainty of the Evidence.Te quality assessments of included studies were conducted by two authors (SH and MV) using the Cochrane risk-of-bias tool.Te tool includes the following seven domains: random sequence generation, blinding of personnel and participants, allocation concealment, blinding of outcomes, selective reporting, incomplete outcome data, and other biases.Studies were categorized as high quality if at least three domains showed low bias potential [25].Te overall certainty of evidence in the studies was graded using guidelines Te overall estimates for the intervention and control groups were calculated based on the mean and SD of BW, WC, and BMI.To calculate efect sizes for all variables, weighted mean diferences (WMDs) were applied along with 95% confdence intervals (CIs) [26].Cochran's Q test was quantifed using the inconsistency index (I-squared) to assess heterogeneity between studies [25].Studies with high heterogeneity were identifed by I 2 ≥ 50% and P value of Q statistic <0.1 [27].Subgroup analyses have been performed to investigate possible sources of heterogeneity.A sensitivity analysis was performed to examine the infuence of any single study or group of studies on the results [28].Publication bias was assessed using funnel plots and Begg's and Egger's tests [28].In addition, a metaregression analysis was performed to examine the relationship between the estimated efect size and the trial duration and sample size.

Results of the Search.
A total number of 789 articles were identifed at the end of the primary search of databases.Te title and abstract of each record were screened after removing 130 duplicates, resulting in the selection of 26 studies for further assessment.In the next step, 19 studies were excluded based on the full-text review.Tese eliminations were due to the following reasons: administered purslane in combination with other components (n � 6), those without a placebo group (n � 5), and trials that did not provide sufcient data for outcomes (n � 8).Finally, seven studies were included in this systematic review and metaanalysis [17,22,23,[29][30][31][32].Te fow diagram of the literature search process is shown in Figure 1.

Study Characteristics.
Te total number of detected trials according to the type of variables was as follows: seven studies for BW, seven studies for BMI, and fve studies for WC.Te important characteristics of the seven included trials are summarized in Table 1.Tese trials were published from 2007 to 2018 and conducted in Iran [17,22,23,29,30,32] and Israel [31].Te sample size in the included studies ranged from 20 to 71.Daily dosage of purslane varied between 180 and 10,000 mg, and duration of purslane supplementation varied from 8 to 12 weeks.In total, 374 participants were enrolled in these trials, of which 220 individuals were allocated to the purslane supplementation group and 226 subjects to the control group.Te mean age of the participants ranged from 22.1 to 58.3 years old, and the mean baseline BMI varied from 26.30 to 32.70 kg/m 2 .Te study participants included patients with MetS [23], type 2 diabetes (T2DM) [17,31], asthma [32], nonalcoholic fatty liver disease (NAFLD) [22,29], and obese or overweight women [30].All trials were conducted on both genders except for two studies that were done exclusively on women [23,30].Regarding changes in BW, three studies [17,22,23] reported a signifcant reduction, while four studies did not fnd such an efect.According to the current systematic review, three studies reported a decrease in BMI with purslane [17,22,30], while three studies failed to fnd any signifcant efect on BMI.Few trials evaluated the efect of purslane on WC.Based on their results, two trials reported a favorable efect of purslane intake on WC reduction [22,23], while others found no signifcant efect.

Risk-of-Bias Assessment and GRADE Assessment.
Te results of the quality assessment of the included trials are available in Figure 2. Te GRADE profle for the certainty of the evidence is included in Supplementary Table 2. Te moderate quality of BW and BMI was due to serious limitations in indirectness.In addition, WC was considered low quality due to serious limitations in imprecision and indirectness.

Te Efects of Purslane Supplementation on BW.
Seven eligible studies, with a total of 379 participants, investigated the efect of purslane supplementation on BW.BW signifcantly decreased in the purslane group showed a signifcant decrease in BW compared to the control group (WMD: −0.94 kg, 95% CI: −1.57-−0.31,and P � 0.002), with signifcant heterogeneity among the trials (I 2 � 68.9% and P � 0.004) (Figure 3).Subgroup analyses revealed a more pronounced reduction in BW with purslane supplementation based on the following factors: the type of purslane product (extract), the duration of the intervention (8 weeks), the gender of the participants (female), and the health status (overweight or obese) (Supplementary Table 3).

Te Efects of Purslane Supplementation on BMI.
Seven eligible studies, with a total of 379 participants, investigated the efect of purslane supplementation on BMI.Purslane supplementation signifcantly decreased BMI (WMD: −0.53 kg/m 2 , 95% CI: −0.88-−0.18,and P < 0.001) (Figure 4).Tere was signifcant between-study heterogeneity (I 2 � 842.7% and P < 0.001).Subgroup analysis showed that purslane supplementation had a stronger efect on BMI in trials that met the following criteria: duration of treatment was 8 weeks, type of purslane product was extract, participants had MetS or obesity, mean age of participants was less than 40 years old, sample size was more than 60, and trials involved only female subjects (Supplementary Table 4).

Te Efects of Purslane Supplementation on WC.
Five eligible trials, with a total of 296 participants, investigated the efect of purslane supplementation on WC.Te purslane group did not show a signifcant reduction in WC compared to the control group (WMD: −0.28 cm, 95% CI: −1.47-0.91,and P � 0.23), with high heterogeneity among the studies (I 2 � 83.6% and P � 0.035) (Figure 5).In Journal of Food Biochemistry the subgroup analysis, the sample size, duration, gender, and health status of study participants explained this heterogeneity.Subgroup analysis indicated that purslane supplementation had a greater efect on WC in trials that met the following conditions: duration of treatment was 12 weeks, participants had MetS or obesity, and sample size was more than 60 (Supplementary Table 5).

Metaregression.
To evaluate the infuence of potential moderators on the estimated efect size, a meta-regression analysis was performed.Findings from the linear association revealed that the duration of treatment and sample size had no association with BW, BMI, and WC (Supplementary Figures 1a-1f ).
3.6.Sensitivity Analysis.Te sensitivity analysis results indicate that the overall estimates for BW, BMI, and WC remained unafected by the exclusion of any individual study (Supplementary Figures 2a-2c).

Publication Bias.
Visual inspection of the funnel plots indicated evidence of moderate asymmetry in the efects of purslane supplementation on obesity indices.In contrast, Egger's regression tests provided no evidence of publication bias for BW (P � 0.597), BMI (P � 0.539), and WC (P � 0.942) (Supplementary Figures 3a-3c).

Discussion
Tis meta-analysis is the frst to evaluate the efect of purslane supplementation on obesity indices in adults.Te fndings indicated that purslane supplementation signifcantly decreased BW and BMI.A greater reduction was observed in some subgroups, such as those conducted on females, those lasting eight weeks, those using extracts, and those conducted on obese or MetS patients.However, this meta-analysis showed that purslane supplementation cannot afect WC in comparison with the control group, which may be attributed to the limited number of trials.Nevertheless, subgroup analysis showed that purslane supplementation signifcantly lowered WC in longer-term studies (12 weeks) and those with a larger sample size (≥60).On the other hand, the fndings based on only two studies showed that purslane supplementation increased WC in eight weeks.Te limited number of studies within each category may potentially result in biased estimates of treatment efects.As such, the fndings should be interpreted with caution due to the small number of trials included in the analysis.

Journal of Food Biochemistry
Purslane has been used as a traditional medicine in various cultures for its health-promoting efects on disorders related to gastrointestinal, respiratory, hepatic, renal, neurological, and infectious diseases [33].Its potential health benefts have been extensively studied in recent years, leading to a growing interest in its use as a functional food [34].Tis meta-analysis assessed the efects of this plant on obesity indices and found a large and medium infuence on BW and BMI, respectively.Tese results were similar to a clinical trial without a control group that was not included in the present analysis [21].Tis study investigated the effects of 10 g of purslane seeds on T2DM patients and reported decreased BW and BMI after eight weeks of supplementation compared to the baseline.Moreover, some of the individual studies included in this analysis reported results that are in line with our fndings [17,23,30].For example, Ghorbanian et al. [30] indicated that 1200 mg purslane in the form of a supplement could efectively reduce BMI in obese or overweight women.However, in patients with asthma disease, 10 g of purslane seeds for eight   weeks had no impact on BW, BMI, and WC, except for hip circumference [32].Aliniya et al. [35] also reported no efect of 1 g/day purslane supplementation for 12 weeks on BMI, body fat percentage, and waist-to-hip ratio compared to control in obese postmenopausal women with NAFLD.In another study without a control group, 6 g/day purslane supplementation for four weeks did not change the BW of normal-weight hypercholesterolemic adults [36].Diferences in the study population, as well as the dose and duration of supplementations, may account for this conficting evidence.Te fndings are also supported by a meta-analysis including 10 randomized, double-blind, placebo-controlled studies showing that supplementation with alpha-lipoic acid (ALA), a supplement with antioxidant properties, can lower BMI and BW [37].In another meta-analysis, the ALA supplement signifcantly reduced BW and BMI compared with a placebo group, but its efects on WC were not signifcant [38].In this meta-analysis study, it was also found that weight loss was greater in studies lasting less than 10 weeks compared to longer-term studies [38].In prior open-label studies, ALA supplementation has been shown to efectively reduce the weight of overweight and obese individuals [39,40].In addition, the presence of thiamine in purslane may explain why purslane could be more efective in obese, MetS, and diabetic patients.Tiamin is a coenzyme that plays an important role in converting carbohydrates, fats, and proteins into energy, and studies indicate that obese and diabetic patients often have low levels of thiamin [21,41,42].Hence, purslane consumption may help to alleviate this thiamine defciency.

Journal of Food Biochemistry
Te results are also consistent with the fndings of previous studies conducted on animal models.Jung et al. [43] investigated the efects of a diet containing 5% and 10% purslane powder on high-fat diet-induced obese mice and demonstrated reduced weight gain and visceral fat with a high dose after 12 weeks.In a diferent study, administering fresh purslane for eight weeks reduced the adipose tissue weight in obese albino rats [44].However, Won and Kim found no signifcant efect of orally administering 75 and 125 mg/kg of the ethanol extract of purslane for four weeks on weight gain and feed intake in male C57BL/6J mice with high-fat diet-induced obesity.Nevertheless, they reported a signifcant improvement in the feed efciency ratio (BW gain/food intake) with purslane administration [45].Te contradictory evidence could partially be attributed to the diferences in the dose and duration of purslane supplementation and the type of used animals.
Purslane has been associated with plausible mechanisms that have antiobesity efects.Given the signifcant roles of oxidative stress and infammation in the development and progression of obesity, the potential protective efects of purslane against obesity and its related complications could be attributed to its antioxidant and anti-infammatory properties [18,46].Te previous literature has also suggested that purslane can positively impact insulin resistance [47], leading to potential improvements in weight management [48].Furthermore, purslane could stimulate AMPactivated protein kinase (AMPK) phosphorylation in adipocytes [49].AMPK acts as a cellular regulator of energy homeostasis.Its activation in the adipose tissue stimulates the browning process, energy expenditure, glucose uptake, adiponectin secretion, and fatty acid oxidation, while simultaneously suppressing lipogenesis, lipolysis, and secretion of proinfammatory markers [50,51].Terefore, AMPK activation by purslane protects against obesity and its associated metabolic dysfunctions.Te supplementation of purslane has also been linked to the upregulation of hepatic peroxisome proliferator-activated receptor (PPAR)-α [43,52], which is known to suppress the growth and differentiation of adipocytes while promoting lipolysis and fatty acid oxidation [53].As another potential mechanism, fresh purslane could increase hepatic cholesterol 7ahydroxylase (CYP7A1) expression and, subsequently, bile acids formation [44].
Evidence supports the benefcial efects of bile acids on improving various parameters associated with MetS [54].Te bioactive components in purslane, including carotenoids, favonoids, saponins, omega 3, and thiamin, are thought to be responsible for its antiobesity efects [55].Te administration of homoisofavonoids extracted from purslane to 3 T3-L1 preadipocytes resulted in a reduction in lipid accumulation as well as the downregulation of adipogenic transcription factors, including PPAR-c and CCAAT/enhancer-binding proteins (C/ EBPα), along with adipogenic target genes [56].However, further research should be conducted to shed light on the other associated mechanisms of the antiobesity efects of purslane.

Side Efects.
Only a few studies have assessed the potential side efects of purslane.It has been reported that purslane contains high levels of oxalate, which can lead to hyperoxaluria and an increased risk of calcium oxalate crystals and kidney stones [57].A recent case report discovered that the consumption of 0.75 kg of purslane in a single meal led to oxalate nephropathy [58].It is suggested that consuming purslane alongside yogurt may reduce the absorption of soluble oxalate [57].Nevertheless, it is still questionable to recommend daily consumption of purslane.

Strength and Limitations.
Tis study was the frst to systematically assess the efects of purslane on obesity indices.Te present study was conducted strictly according to the PRISMA guidelines [24] and observed signifcant efects of purslane on BW and BMI.No evidence of publication bias was observed in this meta-analysis, as determined by the Egger regression test [28].In addition, exploring the sources of heterogeneity and assessing the certainty of evidence are other strengths of this study [59].Te evidence for BW and BMI was graded as having moderate certainty.However, it is important to acknowledge several limitations that should be taken into consideration when interpreting the results.First, there was signifcant methodological and statistical heterogeneity among the included studies [59].Tis heterogeneity was particularly evident in the form of purslane supplementation, which varied from seeds [17,22,23,30,32] to extracts [29][30][31] across studies.Second, a limited number of studies and participants were involved in the analysis [17,22,23,[29][30][31][32].Tis limitation is especially relevant when considering WC, as only fve studies [17,22,23,29,32] were available for analysis.Tird, most of the included studies were performed in Iran [17,22,23,29,30,32], which may restrict the generalizability of the fndings to other regions and populations.Finally, it should be noted that most of the studies included in meta-analysis focused on diverse health conditions such as MetS [23], T2DM [17,31], asthma [32], NAFLD [22,29], and obese or overweight women [30] and did not have a primary aim of examining the antiobesity efects of purslane [17,22,23,[29][30][31].

Conclusion
Tis meta-analysis concludes that purslane supplementation has a signifcant efect on BMI and BW but not on WC in adults, indicating its potential therapeutic use.However, subgroup analysis showed that purslane supplementation signifcantly lowered WC in longer-term studies (12 weeks) and those with a larger sample size (≥60).Furthermore, the pooled results of previous RCTs showed that purslane is a safe and efcacious intervention for reducing obesity indices in subjects with MetS or obesity.Terefore, the consumption of purslane may have indirectly contributed to the amelioration of clinical symptoms in diseases with metabolic disorders, owing to its impact on some obesity indices.However, given the limitations and the low number of included studies in the present meta-analysis, more large-scale RCTs with better methodological designs are warranted to confrm the efcacy and safety.
bias Unclear risk of bias High risk of bias

Figure 2 :
Figure 2: Results of risk-of-bias assessment for trials included in the current meta-analysis on the efects of purslane supplementation on obesity indices.

Figure 3 :
Figure 3: Forest plot illustrating weighted mean diference and 95% confdence intervals for the impact of purslane on BW.

Figure 4 :
Figure 4: Forest plot illustrating weighted mean diference and 95% confdence intervals for the impact of purslane on BMI.

Figure 5 :
Figure 5: Forest plot illustrating weighted mean diference and 95% confdence intervals for the impact of purslane on WC.

Table 1 :
Characteristic of included studies in the systematic review and meta-analysis.