ReviewThe effect of glucomannan on body weight in overweight or obese children and adults: A systematic review of randomized controlled trials
Introduction
The prevalence of obesity is reaching epidemic proportions. The first-line treatment (i.e., promoting a healthy diet and regular physical activity) is difficult to follow. There is continuous research into the modalities complementing lifestyle modifications that are helpful in the reduction of body weight (BW). Due to the prevalent use of over-the-counter products advertised as being effective in promoting weight loss, evidence is needed to confirm the claimed effects. One of the dietary supplements used is glucomannan (GM), a soluble fiber derived from the plant Amorphophallus konjac. Its potential mechanism of action is to increase satiety due to a delay in gastric empting caused by the “mass effect” of the viscous, gel-like mass forming in the stomach and slowing down gastrointestinal transit time [1]. In 2010, the European Food Safety Authority (EFSA) confirmed the positive effect of GM on the reduction of BW in overweight adults. The effect was achieved when ≥3 g of GM was supplemented daily in three doses of 1 g together with one to two glasses of water before a meal. However, at that time, the EFSA did not confirm the effect in children [2]. Similarly, an expert panel sponsored by the U.S. National Heart, Lung, and Blood Institute stated that “glucomannan does not significantly improve weight loss” in children [3].
In many European countries, GM is being widely marketed for the management of overweight or obesity. Given the scarcity of data and somewhat conflicting recommendations, we decided to conduct a randomized controlled trial (RCT) assessing the weight loss effect of GM supplementation in children. However, as previously noted, a systematic review of the literature should precede the conducting of new research [4].
A systematic search has been conducted to evaluate the clinical effectiveness of supplementation with GM; the researchers concluded that it beneficially affected total cholesterol, low-density lipoprotein cholesterol, triglycerides and BW, but not high-density lipoprotein cholesterol or blood pressure [5]. As more than 5 y have passed since that review was published, we aimed to systematically evaluate the current evidence on the effect of GM supplementation on BW reduction as our main point of interest. We aimed to exclude studies referring to patients with diabetes mellitus, hypertension, or other chronic conditions requiring drug treatment. This decision was made to better define the effect of GM supplementation in the population we aimed to address in the planned interventional trial (i.e., obese or overweight, otherwise healthy individuals).
Section snippets
Review protocol
The methods planned at each stage of this review were specified in advance and documented. However, formally, the review protocol was not registered.
Criteria for eligibility
Participants had to be children or adults who were overweight/obese (according to our definition). To increase the homogeneity, we decided not to include studies performed in populations with predefined diabetes mellitus or hyperglycemia, as well as in other populations with diagnosed diseases requiring drug treatment. All studies that assessed the
Search results and characteristics of studies
Figure 1 presents a flowchart documenting the study selection process. Two registered studies were identified in clinicaltrials.gov (one ongoing and one of unknown status); for their characteristics, see Supplementary Table 1. The Table summarizes the key characteristics of the six included trials (RCTs). Five studies are of parallel design [8], [9], [10], [11], [12] and one is a crossover design [13]. The participants included were children (one RCT, N = 60) [10] and adults (five RCTs,
Principal findings
The objective of this review was to update evidence on the effect of GM supplementation on BW compared with administration of a placebo. A statistically significant reduction in BW was observed in three studies. In the first one, the transient effect was seen after 2 wk, but it did not last until the end of the 8-wk intervention [9]. Another study, on the contrary, reported a significant difference between groups in BW reduction in favor of GM after both 4 and 8 wk of treatment [12]. An effect
Conclusion
In overweight or obese, otherwise healthy adults, there is limited evidence that GM supplementation may help to reduce BW, but not BMI. Limited data do not allow one to draw any conclusions with regards to the effect of GM supplementation in children.
Studies of proper methodological design, consisting of larger study groups with longer (>12 wk) interventions and follow-up periods, are needed, especially in children, to establish whether the BW-reducing potential of GM is clinically significant.
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2022, Micro- and Nanoengineered Gum-Based Biomaterials for Drug Delivery and Biomedical ApplicationsCan konjac (Amorphophallus konjac K. Koch) and it constituent glucomannan be useful for treatment of obesity?
2021, Obesity MedicineCitation Excerpt :In animal experiments, konjac or glikomannan treatment decreased the levels of blood glucose, serum insulin, glucagon-like peptide 1, glycated serum protein, total cholesterol, triacylglycerols, low-density lipoprotein cholesterol, and non-esterified fatty acid and reduce adipose cell hypertrophy via promotion oif glycerolipid (diacylglycerol, monoacylglycerol, and triacylglycerol), fatty acyl (acylcarnitine and hydroxyl fatty acid), sphingolipid (ceramide and sphingomyelin), and glycerophospholipid (phosphatidylcholine) metabolism (Chen et al., 2019). Reduced weight after intake of 2–4 g of glucomannan was determined in adult patients suffering from obesity (Keithley and Swanson 2005; Sood et al., 2008; Zalewski et al., 2015). Critical analysis of the relevant publications by other authors (Onakpoya et al., 2014), however, did not determine a definitive and statistically significant positive effect of glucomannan on body weight in adults with obesity.
This study was fully funded by the Medical University of Warsaw. HS was responsible for the study concept and supervision. BMZ and AC were responsible for acquisition and analysis and interpretation of data, as well as for drafting of the first draft of the manuscript. All the authors took part in the study design and critical revision of the manuscript for important intellectual content. The authors have no conflicts of interest to report.