The gut microbiome is emerging as an important regulator of metabolic health and energy homeostasis (1). Derrien called the microbiota “the X-factor” that may account for the highly individualized responses to dietary interventions (2). Dietary interventions, including probiotics, prebiotics, and dietary fat, constitute one of the main strategies for modulating the gut microbiota composition and activity (3–5). Specifically, dietary fat has been shown to have a significant impact on gut microbiota whose function and clinical implication in obesity are well-documented and pose the question if dietary fat binders could contribute toward the growth of healthy gut microflora (6, 7). While studies on the microbiome and its link to obesity are compelling, we have yet to see interventions that describe significant weight loss and improved metabolic biomarkers combined with favorable shifts in the profile of the microbiota. This study describes the clinical effect of a novel formulation IQP-AE-103, consisting of a blend of two natural principal ingredients that have unique properties and can bind dietary fat synergistically in an in vitro setting.

The ratio of phyla Firmicutes to Bacteroidetes in mice and humans has been identified to be different in obese and lean phenotypes. Relative abundance of Firmicutes and a reduction in Bacteroidetes appears to correlate with greater efficiency in energy harvested by the microbiota and thus has been associated with the obese population (8). This study demonstrated that individuals with a high Firmicutes to Bacteroidetes ratio may extract as much as 30% more calories from the same portion of food as those with a lower ratio. This gut dysbiosis may be more likely to foster an energy net positive metabolic environment, leading to increased fat storage, greater resistance and individual variability to therapeutic interventions (9). Additionally, new research has also linked certain species or strains of organisms with leaner body types. The abundance of Akkermansia muciniphila is inversely associated with negative metabolic markers, including fasting glucose levels, waist-to-hip ratio, subcutaneous fat deposition, and obesity. Elevated Akkermansia levels in combination with greater microbial gene richness are indicative of a diverse microbiome. These elevated levels are not only more likely to be present in lean individuals, but they are also strong indicators of the subjects most likely to experience significant change with the best metabolic outcomes (10, 11). Dao showed that subjects with high levels of A. muciniphila at baseline had the most significant improvement in insulin sensitivity and other positive metabolic changes (12). While Dao demonstrated significant metabolic improvements after 6 weeks of a calorie-controlled diet and 6 weeks of a maintenance diet, subjects did not experience corresponding changes in weight (12). A 2019 intervention study using A. muciniphila similarly showed several metabolic parameters improved but did not result in statistically significant weight loss, changes in body mass index (BMI), or visceral fat deposition (11).

In a previously published, double-blind, placebo-controlled, 12-week trial, overweight and moderately obese subjects on a hypocaloric diet were treated with IQP-AE-103 (13). IQP-AE-103 is a combination of dehydrated powder of okra pods [Abelmoschus esculentus (L.) Moench] and inulin, a heterogeneous mixture of fructose polymers extracted from chicory roots (14, 15). This study demonstrated significant weight loss, a reduction in feelings of hunger, and a decrease in BMI, body fat mass, and waist and hip circumference as compared with the placebo (13). Much of the noted benefits were thought to be the result of the dietary fat binding by IQP-AE-103 and the physicochemical swelling and gel-forming properties of okra pods, which have been shown to induce satiety in vivo (13). A review of satiety-inducing polysaccharides showed that satiety was typically noted at doses of 8–10 g or more, making the satiety effect in Uebelhack’s study unique for its combined, low, daily dose of 2,490 mg (16, 17).

Carbohydrates are the most abundant macronutrient in okra pods and include both soluble and insoluble fibers (18). Okra contains highly viscous, soluble, indigestible polysaccharides, such as pectin, with strong swelling and gel-forming properties (15). Moreover, okra pods and seeds may contain several unique polyphenols, including flavonoids, isoquercitrin, and quercetin-3-O-gentiobiose (19). Okra pods contain up to 6.7% polyphenols, mostly found in the seeds (20).

In contrast, inulin is a soluble, indigestible, but non-viscous polysaccharide with less or no gel-forming properties that are rapidly fermented by the microbiota (21). Inulin and other soluble, indigestible fibers have been extensively studied for their benefits associated with glucose homeostasis, lipid regulation, colon disease prevention, and transit time, (22–30). However, clinical outcomes for inulin supplementation and weight loss are mixed. For example, Guess’s study of 30 g/day in pediatric subjects resulted in a 7.6% reduction in weight over 18 weeks (compared with 4.9% in the placebo) (31). Another study supplemented 10 g of inulin plus 10 g of resistant maltodextrin in combination with a caloric restriction and showed no significant weight loss over the placebo (32). IQP-AE-103 provided a small dose, 510 mg/day, of inulin in combination with dehydrated okra powder and showed clinically proven weight loss (13).

Deleterious gut microbiota modulation was previously thought to be a consequence of weight gain and other metabolic disturbances. However, emerging science is confirming that microbiota shifts may also contribute to causation as well as be the consequence of the hallmarks of metabolic disease (33). Studies have shown that gut microbial diversity and composition in humans is more significantly modified by dietary and/or environmental factors than genetics (34).

This study demonstrates that IQP-AE-103 leads to both a significant reduction in Firmicutes abundance and a significant increase in A. muciniphila, specifically in subjects who achieved at least 5% of weight loss. This shift in microbiota indicates that the fat-binding properties of inulin and okra not only exert an action on body weight but also contribute to the increase in diversity of the gut microflora.

A total of 36 subjects were randomized into each study arm. Due to subjects’ dropouts or mishandling of samples, six fecal samples from the IQP group and eleven samples from the placebo group were not included for microbiome analysis (Figure 1). Thus, the fecal samples of thirty subjects in the IQP group and twenty-five subjects in the placebo group were analyzed. Due to the unavailability of fecal samples from certain subjects at baseline or at the end of the study, the intention-to-treat population analysis was not performed. The per-protocol analysis was performed only on subjects with complete fecal samples.

The mean age of the study population was 48.67 ± 11.69 years. The proportion of women to men was higher in both groups. There were no statistical differences in age, gender distribution, body height, body weight, BMI, waist circumference, hip circumference, body fat mass, fat-free mass, and energy requirements between the study groups at baseline. All subjects who completed the study met the compliance rate (≥80 to ≤120%) for intake of investigational products. Clinical baseline characteristics are summarized in Table 2.

After 12 weeks of intervention, body weight was significantly reduced in the IQP group compared with the placebo group, 5.16 ± 2.39 kg vs. 0.97 ± 2.09 kg (p < 0.001). In addition, 17 (57%) subjects in the IQP group lost at least 5% of their baseline body weight compared with only 1 (4%) subject in the placebo group. The mean body weight reduction in the subgroup of subjects who lost at least 5% body weight from the IQP group (hereafter referred to as IQP5) was 6.74 ± 1.94 kg and was significantly greater compared with the placebo group (p < 0.001). There were also significant differences in mean reduction of BMI, waist circumference, hip circumference, and body fat mass between the IQP and placebo groups, as well as between the IQP5 and placebo groups. Furthermore, significant differences were also observed in some of these parameters at weeks 4 and 8 between the groups. Results are summarized in Table 3.

The characterization of the microbiota communities present in fecal samples collected prior to the start of the intervention (week 0) and at the end of the study (week 12) was performed to investigate changes in gut microbiota composition. The relative abundances of 13 phyla were analyzed, and the five most dominant phyla (Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, and Verrucomicrobia) are presented in Figure 2. At baseline, the placebo group had the highest relative abundance of Firmicutes (76.15 ± 8.83%), while the IQP5 group had the highest relative abundance of Bacteroidetes (17.91 ± 9.40%) and Actinobacteria (6.28 ± 5.42%), respectively. After 12 weeks, all groups had a decreased relative abundance of Firmicutes, and the placebo group had the highest relative abundance (73.24 ± 8.06%) amongst the three groups. Differences in the relative abundance of Firmicutes in the IQP group (66.96 ± 10.74%) and IQP5 group (66.22 ± 11.75%) were significant in comparison to the placebo group (p < 0.05). The relative abundance of Bacteroidetes and Actinobacteria was highest in the IQP (19.60 ± 9.77%) and IQP5 groups (7.46 ± 4.55%), respectively; however, the differences in comparison to the placebo group were not statistically significant. Statistical changes from baseline within groups were observed in the IQP (Verrucomicrobia), IQP5 (Verrucomicrobia), and placebo (Firmicutes and Proteobacteria) groups.

Data from the computed Firmicutes/Bacteroidetes (F/B) ratio was higher in the IQP group (19.25 ± 65.74) compared with the placebo group (9.0 ± 17.15) at baseline. In contrast, the F/B ratio of the IQP5 group (6.79 ± 7.65) was lower than the placebo group. After 12 weeks, the F/B ratio of the IQP and placebo groups were reduced to 4.54 ± 2.96 and 5.78 ± 3.41, respectively. Similarly, the F/B ratio of the IQP5 group was reduced to 5.28 ± 3.29. The F/B ratio was reduced in all three groups after 12 weeks from baseline and a distinguished reduction was observed in the IQP group; however, differences between the groups (IQP vs. placebo and IQP5 vs. placebo) were not statistically significant.

Next, Lefse analysis was performed to identify bacterial taxa distributions that are significantly and statistically different (p < 0.05) among the groups with an effect size [linear discriminant analysis (LDA) score] higher than 2 at different phylogenetic levels. The differences in the overall microbiota composition and abundance distribution in the IQP group vs. the placebo group and the IQP5 group vs. the placebo group are shown in the biomarker plots in Figures 3A,B. The placebo group overall had a lower microbiota composition and a less diversified microbiota community. The IQP and IQP5 groups were more enriched with several microbiota groups, for example, family Actinomycetaceae, family Mycobacteriaceae, genus Prevotella, genus Lactococcus, and genus Akkermansia (for the IQP5 group). In contrast, the family Lachnospiraceae and the genus Ruminococcus were more prevalent in the placebo group.

Furthermore, analyses on the relative abundance of A. muciniphila were performed to investigate the association of the microbiota with the intake of IQP-AE-103 and effect on weight reduction. A. muciniphila was at least 4-fold higher in the IQP5 group than in the placebo group (2.91 ± 4.12% vs. 0.63 ± 1.43%; p < 0.05) after 12 weeks. No significant difference was observed in the abundance of these microbiota at baseline. Statistical changes from baseline within the group were also observed in both the IQP and IQP5 groups, but not in the placebo group (Figure 4).

In summary, the intake of IQP-AE-103 reported a significant reduction in body weight, BMI, body fat mass, waist circumference, and hip circumference. Furthermore, the IQP weight loss population had a distinct and differentiated microbiota diversity and a significant difference in the relative abundance of microorganisms such as Firmicutes and A. muciniphila in comparison to the placebo group.

This study is unique in reporting both significant weight loss and corresponding favorable shifts in Firmicutes and A. muciniphila, both of which are associated with better metabolic health (39–42). Similar to other studies, and in line with positive improvements in the metabolic profile, both Lefse and microbial relative abundance analyses showed that Firmicutes abundance was significantly lower in the IQP group compared with the placebo group at the end of the study (11, 12, 43).

At least 5% of weight loss was observed for 57% of subjects with IQP-AE-103 supplementation (referred to as 5% responders or IQP5). Analysis of this subgroup showed that there was also a significant increase in A. muciniphila of 300% over baseline and over 460% over placebo after 12 weeks. This subgroup also demonstrated a similar decrease in Firmicutes both over baseline and placebo.

While other studies investigating dietary supplementation with inulin have certainly shown a positive impact on gut microbiota, the administered dose per day of inulin has been high, ranging from 8 to 30 g, with 10 g being the average (44, 45). The dose of IQP-AE-103 in this study provided 510 mg/day of inulin. While inulin has been associated with an increase in A. muciniphila in both healthy and overweight and obese subjects (46), there are no other clinical studies demonstrating a reduction in weight and/or a change in A. muciniphila at this dose, alone or in combination with other ingredients. This low dose of inulin synergistically combined with okra powder provides similar benefits as previously reported at higher doses and without the adverse events traditionally associated with inulin, like abdominal gas and bloating or laxative effect. IQP-AE-103 had excellent tolerability, and no adverse events related to the intake of IQP-AE-103 were reported after 12 weeks of intervention (13).

Research has been accelerated on the use of A. muciniphila as a potential therapeutic agent for metabolic and gastrointestinal disorders, including obesity (47). The deleterious effects of a high-fat diet have been shown to be offset by Akkermansia enriching polyphenols, including positive modulation of intestinal gene expression, improved lipid regulation, enhanced insulin sensitivity, reduced fat deposition, and increased epithelial integrity (11, 12, 48, 49).

In 2019, the first preliminary clinical trial supplementing Akkermansia (live and sterilized organisms) as a targeted therapy was published. Treated subjects showed improved insulin sensitivity, reduced insulinemia and plasma, and reduced total cholesterol. Although Akkermansia levels showed a positive trend, the study did not achieve significant changes in body weight, fat mass, or hip and waist circumference (11). While very promising, it reinforces work previously published that confirms A. muciniphila’s modulation and effect are likely mediated by multiple and potentially confounding factors, including variations in diet (macronutrients as well as calories), nutritional status, host health, lumen environment, ethnicity, gender, age, medication use, mucin structure, and availability, as well as baseline abundance of Akkermansia and other organisms (12, 30, 50–58). These confounding factors, which contribute to modulating Akkermansia, may offer further explanation for many of the conflicting data noted in previous publications.

There are multiple studies in animals and humans that correlate a higher abundance of A. muciniphila with a lean phenotype (42, 52, 58–63). Additionally, fecal transplant studies have demonstrated that transferring the microbiota of lean or obese animals into the opposite phenotype results in the animals trending toward or adopting the metabolic state of the donor (64–68). Studies on prebiotic fibers and their impact on Akkermansia in humans are mixed (46, 69). While it is clear that a strong connection exists between the microbiota profile and metabolic health, there are few studies that actually demonstrate weight loss with fiber supplementation even when there is clearly a positive shift in the microbiome (11, 32, 70–72).

Akkermansia levels have been positively influenced in other human studies through caloric restriction, gastric bypass, and polyphenol, inulin, polydextrose, and yeast fermentate supplementation. However, with the exception of gastric bypass, none of these studies showed a concomitant change in weight or BMI (10, 57, 73–76). In type 2 diabetics, caloric restriction increased levels of A. muciniphila by 125% (57). Similarly, Dao showed a correlation between a reduced-calorie diet in obese and overweight subjects and an improved abundance of A. muciniphila. In this study, an increase in Akkermansia was only noted in individuals with a below median and baseline levels of the microorganism (12). Even more surprisingly, subjects with a high starting level (above the median) of A. muciniphila had a decrease in abundance over the course of the study.

Interestingly, Healey showed that changes in the microbiota profile were linked to dietary intervention, specifically demonstrating that subjects consuming a high fiber diet plus 16 g of inulin-type fructans/day were much more responsive to favorable shifts in their microbiota profile than those on a low fiber diet and 16 g of inulin per day. Overall, dietary records showed that the high dietary fiber group had slightly higher energy, fat, carbohydrate, and fiber intake as compared with the low dietary fiber group (77).

In this study, the protocol diet was intended to reduce calories and standardize the amount of fat intake among all the participants. While suggested menus were provided, subjects’ macronutrient consumption could vary while still meeting the caloric and fat requirements. Previous studies showed that macronutrient dietary makeup may also have a profound impact on the susceptibility of the microbiota for change, including total calories, fat, fiber, and refined carbohydrate levels (6, 7, 78). In our study, both subject groups were provided with standardized calorie and fat intake, and a positive shift in the growth of healthy gut microflora was only seen in the IQP group and more prominently in subjects with at least 5% of baseline body weight loss after taking dietary fat binder.

One of the limitations of this study could be the small sample size. The sample size was determined primarily for the weight loss effect by the Cohen’s effect size (group comparison), for the significance level of 5.0% (double-sided) and power of 80% (79). In consideration of the use of non-parametric statistical analysis, the necessary sample size was 28 subjects per study arm and was further increased to 36 subjects after consideration of dropout rate (20%) and block randomization requirements. The observed changes in the microbiome remain interesting for exploratory purposes, and the research findings warrant further study with a larger sample size.

In fact, some studies indicate that shifts in the microbiota may occur on the first day of dietary change or supplementation (80), and positive changes in the abundance of A. muciniphila can occur in as short as 3 days (80). Certainly, the microbiota shift occurs prior to the time point of statistically significant changes in weight loss. This supports the emerging theory that changes in the microbiota, and perhaps even specific species, may contribute to the etiology of weight changes rather than be the result of the weight changes (81).

To the best of our knowledge, we report the first, controlled study in humans where an OTC supplementation resulted in both favorable changes in Firmicutes and Akkermansia, as well as corresponding, clinically relevant changes in weight, adiposity, and body mass index. This shift in microbiota indicates that the fat-binding properties of the synergistic blend of dehydrated okra powder and inulin not only exert an action on body weight but also on gut microflora diversity.

The data generated from this study is not made available to the public due to local ethical guidelines. Further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by the Charité – University Medicine Berlin. The patients/participants provided their written informed consent to participate in this study.

LP, PD, and PC were involved in the conceptualization and design of the study. LP performed further data analyses. LP and JC wrote the manuscript. PD and PC critically reviewed and contributed to the final content of the manuscript. All authors reviewed the data and statistical analyses provided by the independent statistician, contributed to the final content, and approved the manuscript.

LP, PD, and PC are the employees of InQpharm Group that funded the study. InQpharm Group was not involved in the conduct of the trial or the collection of data. JC received consultation fees for the independent review of the data and contributed to the manuscript writing.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.