Resistant starch intake facilitates weight loss in humans by reshaping the gut microbiota

Development of low glycemic index food products with wheat resistant starch: a review

With the growing recognition of the health benefits associated with GI foods in managing type 2 diabetes and alleviating oxidative stress, wheat-based low-GI foods enriched with resistant starch (RS) emerging as a promising alternative to refined grains in daily diets. This review provides a comprehensive overview of the health benefits of RS, delving into its types, characteristics, and the mechanisms underpinning its resistance to hydrolysis. To enhance the functionality of RS, various modification techniques-encompassing chemical, enzymatic, physical, and combinatory approaches-have been explored to increase RS content in wheat-based foods while improving their sensory attributes. Additionally, the incorporation of phytochemicals and other natural extracts into low-GI food formulations has demonstrated potential to enhance both nutritional and sensory properties. This review also examines market trends for low-GI foods, identifying key challenges in industrial manufacturing processes. By addressing these issues, this work aims to support future research and guide the development of improved standards for low-GI wheat-based food products.

Type 3 resistant starch prepared from euryale ferox alleviated the obesity symptoms via gut microbiota regulation

The type 3 resistant starch (RS3) was obtained from euryale ferox through enzymolysis-autoclaving. The effects of euryale ferox RS3 (ERS) on the body weight, lipid metabolism, inflammatory response, and gut microbiota composition of golden hamsters administered a high-fat diet were determined to assess the potential role of ERS in inhibiting obesity. The purified ERS was in the B + V-type crystal form, which has a great anti-enzymatic structure. Additionally, ERS may promote the growth of beneficial gut microbiota including norank_f_Muribaculaceae and Ruminococcus, while it can inhibit the growth of the gut microbiota including Allobaculum, thus alleviating symptoms of weight gain, fat accumulation, oxidative stress, chronic low-grade inflammation, and liver injury. The above findings laid a theoretical foundation for the application of ERS in specific foods to prevent obesity.

Synergistic regulation of colon microflora and metabolic environment by resistant starch and sodium lactate in hyperlipidemic rats

Type 3 resistant starch (RS3) regulates diet-related metabolic diseases by promoting intestinal short-chain fatty acids (SCFAs) and lactate production, and facilitating microbial lactate-to-butyrate fermentation. However, its precise in vivo mechanism remains unclear. Therefore, we studied the effects of type 3 lotus seed resistant starch (LRS3) and sodium lactate (SL) on colonic microbiota composition, metabolism, and lipid parameters. This study aimed to elucidate the mechanism by which LRS3 and SL modulate colonic microbiota and metabolism to mitigate hyperlipidemia in rats induced by a high-fat diet. Results showed LRS3 increased colonic microbial diversity, shifting the composition towards that of healthy rats. LRS3 intake reduced lactic acid-producing bacteria such as Allobaculum, Collinsella, and Blautia in the colon while promoting SCFAs-producing Ruminococcaceae. SL alone stimulated Lachnospiraceae growth. When both were administered, there was a significant increase in Treponema and Ruminococcaceae. The co-intervention of LRS3 and SL significantly affected lipid metabolism-related metabolites, up-regulating palmitic acid while down-regulating androsterone and phosphatidylcholine (PC) substances PC (14:0/20:4(8Z,11Z,14Z,17Z)), influencing unsaturated fatty acid biosynthesis pathways and inhibiting steroid hormone biosynthesis. Finally, via the microbial-metabolism-lipid correlation network, we identified that LRS3 and SL increased SCFAs production through Treponema and Ruminococcaceae metabolism, influencing organic acid and lipid composition in the colon. This indirectly reduced blood lipid levels in hyperlipidemic rats by modulating intestinal microecology.

Type 3 resistant starch prepared from jackfruit alleviated the hyperlipidemia via gut microbiota regulation

Although resistant starch (RS) isolated from raw starch exhibits established regulatory effects on the mouse gut microbiota and associated hyperlipidemia, critical questions persist regarding RS in heated foods - the predominant form in the human diets, namely, the role of RS from heated food in the regulation of hyperlipidemia through gut microbiota is still unclear. This study evaluated the effects of a RS (jackfruit heated resistant starch, JFRS3) from heat-treated jackfruit native starch (JFNS) on hyperlipidemia in golden hamster gut microbes. Compared with JFNS, JFRS3 developed an irregular block-like shape with numerous grooves, exhibited more ordered structures (R1047/1022: 2.952 and R1022/995: 0.964) and greater crystallinity (relative crystallinity (RC): 21.96 %), and transformed into a C-type crystalline structure. Additionally, JFRS3 demonstrated significant antihyperlipidemic effects, which included an increase in high-density lipoprotein cholesterol (HDLC) levels (4.36 mmol/L) and reductions in triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels (14.39, 4.55, and 4.61 mmol/L, respectively), thereby alleviating liver fatty lesions, reducing fat accumulation, and inhibiting adipocyte enlargement. These effects were closely linked to intestinal microbial changes, such as specific microbial enrichment and enhanced gut microbial diversity, potentially influenced by the structural properties of JFRS3. Furthermore, the consumption of JFRS3 was more effective in slowing weight gain and improving blood lipid profiles compared with raw RS present in JFNS. These findings prove that JFRS3 modulates hyperlipidemia induced by a high-fat diet and contributes to the development of alternative strategies for managing high-fat-diet-associated hyperlipidemia.

The lotus seed starch-EGCG complex modulates obesity in C57BL/6J mice through the regulation of the gut microbiota

The starch-polyphenol complex, identified as RS5-resistant starch, has been shown to regulate the gut environment and inhibit metabolic diseases, including obesity. In a study with C57BL/6 obese mice fed LSE, potential anti-obesity effects were demonstrated through physiological and biochemical assessments, gut microbiota analysis, and mechanistic insights. The study showed that LSE reduced mice body weight, serum total cholesterol, and triglycerides (P < 0.05). Serum inflammatory markers (TNF-α, IL-6, IL-1β) and LPS levels were significantly decreased, while glucose tolerance (AUC reduced by 29.29 %) and insulin sensitivity (AUC reduced by 31.79 %) were improved. Histological analysis indicated reduction in adipocyte size and attenuation of hepatic steatosis. Gut microbiota profiling demonstrated LSE increased beneficial bacteria genera Faecalibacterium, Bifidobacterium, and Akkermansia. This correlated with enhanced SCFA production (acetate 41.53 %, propionate 45.52 %, butyrate 57.49 % increase). These findings demonstrate that LSE exerts anti-obesity effects through modulation of the gut microbiota-SCFA-metabolic axis, supporting starch-polyphenol complexes as functional food candidates.

Clinical translation of microbiome research

The landscape of clinical microbiome research has dramatically evolved over the past decade. By leveraging in vivo and in vitro experimentation, multiomic approaches and computational biology, we have uncovered mechanisms of action and microbial metrics of association and identified effective ways to modify the microbiome in many diseases and treatment modalities. This Review explores recent advances in the clinical application of microbiome research over the past 5 years, while acknowledging existing barriers and highlighting opportunities. We focus on the translation of microbiome research into clinical practice, spearheaded by Food and Drug Administration (FDA)-approved microbiome therapies for recurrent Clostridioides difficile infections and the emerging fields of microbiome-based diagnostics and therapeutics. We highlight key examples of studies demonstrating how microbiome mechanisms, metrics and modifiers can advance clinical practice. We also discuss forward-looking perspectives on key challenges and opportunities toward integrating microbiome data into routine clinical practice, precision medicine and personalized healthcare and nutrition.

Regulation of starch metabolism in banana fruit: Mechanisms shaping the nutritional quality

Bananas are nutrient-rich fruits that provide starch, essential vitamins, and minerals and play significant importance in the global economy through extensive production, trade, and consumption. Nutrient metabolic processes, such as starch-to-sugar conversion, are fundamental in shaping the quality of banana fruits. Starch accounts for 15%-35% of fresh fruit weight, and its degradation mediated by ethylene signaling components can increase sweetness, soften texture, and increase the palatability of banana fruit. This review summarizes recent advances in the regulatory mechanism underlying starch metabolism in banana fruits, highlights key research questions for future investigation, and proposes promising strategies to manipulate starch levels to develop new banana varieties with enhanced nutritional quality.

Beyond soluble and insoluble: A comprehensive framework for classifying dietary fibre's health effects

Despite evolving definitions, dietary fibre classifications remain simplistic, often reduced to soluble and insoluble types. This binary system overlooks the complexity of fibre structures and their diverse health effects. Indeed, soluble fibre is not just soluble but has important qualities such as fermentability, attenuating insulin secretion, and lowering serum cholesterol. However, this limited classification fails to account for dietary fibre diversity and predict their full range of physiological effects. This article proposes a holistic classification framework that accounts for different fibre types and can be used to accurately infer their physiological outcomes. This proposed classification framework comprises of five constituents: backbone structure, water-holding-capacity, structural charge, fibre matrix and fermentation rate. This model more accurately captures the structural and functional diversity of dietary fibres, offering a refined approach to predicting their health benefits.

Bifidobacterium adolescentis FJSSZ23M10 modulates gut microbiota and metabolism to alleviate obesity through strain-specific genomic features

Obesity is a major global public health challenge, affecting billions and serving as a primary risk factor for many chronic diseases. Certain probiotics have shown promise in regulating energy balance and enhancing fat metabolism, offering potential strategies for managing obesity. In this study, we evaluated three strains of Bifidobacterium adolescentis and identified B. adolescentis FJSSZ23M10 as the most effective in alleviating high-fat diet (HFD)-induced obesity. This strain significantly reduced weight gain, improved abnormal serum biochemical indicators, decreased lipid accumulation in adipocytes, and enhanced energy expenditure. Furthermore, B. adolescentis FJSSZ23M10 treatment modulated the gut microbiota, notably increasing the abundance of Bifidobacterium and Faecalibaculum. Untargeted metabolomic analysis revealed that B. adolescentis FJSSZ23M10 uniquely upregulated beneficial metabolites, such as butyrate and pyruvic acid, suggesting its superior metabolic impact. Genomic analysis indicated that B. adolescentis FJSSZ23M10 harbored the highest abundance of unassigned genes and carbohydrate-active enzymes (CAZymes) compared to the other strains, highlighting its superior functional potential. Combining the shared and unique modifications in gut microbiota, metabolites, and genomic annotations, the study highlights that genomic differences among probiotics could shape their effects on gut microbiota and metabolites. Conclusively, the study underscores the critical role of probiotic genomic characteristics in determining their functional efficacy and suggests that the intake of the B. adolescentis FJSSZ23M10 strain with enriched genomic features, such as CAZymes, could represent a novel genomic-based strategy for alleviating obesity through gut microbiota modulation and metabolic regulation.

The Metabolite Indole-3-Acetic Acid of Bacteroides Ovatus Improves Atherosclerosis by Restoring the Polarisation Balance of M1/M2 Macrophages and Inhibiting Inflammation

Emerging research has highlighted the significant role of the gut microbiota in atherosclerosis (AS), with microbiota-targeted interventions offering promising therapeutic potential. A central component of this process is gut-derived metabolites, which play a crucial role in mediating the distal functioning of the microbiota. In this study, a comprehensive microbiome-metabolite analysis using fecal and serum samples from patients with atherosclerotic cardiovascular disease and volunteers with risk factors for coronary heart disease and culture histology is performed, and identified the core strain Bacteroides ovatus (B. ovatus). Fecal microbiota transplantation experiments further demonstrated that the gut microbiota significantly influences AS progression, with B. ovatus alone exerting effects comparable to volunteer feces from volunteers. Notably, B. ovatus alleviated AS primarily by restoring the intestinal barrier and enhancing bile acid metabolism, particularly through the production of indole-3-acetic acid (IAA), a tryptophan-derived metabolite. IAA inhibited the TLR4/MyD88/NF-κB pathway in M1 macrophages, promoted M2 macrophage polarisation, and restored the M1/M2 polarisation balance, ultimately reducing aortic inflammation. These findings clarify the mechanistic interplay between the gut microbiota and AS, providing the first evidence that B. ovatus, a second-generation probiotic, can improve bile acid metabolism and reduce inflammation, offering a theoretical foundation for future AS therapeutic applications involving this strain.

Characterization of a novel type 4 resistant starch from tapioca and its obesity-preventive effects through gut microbiota modulation in high-fat diet-treated mice

The rising pandemic of obesity has received significant attention. Yet, more safe and effective targeted strategies must be used to mitigate its impact on individual health and the global disease burden. While the health benefits of resistant starch (RS) are well-documented, the role of RT-90 (a phosphate-modified tapioca RS containing 90.1 % total dietary fiber) in mitigating obesity remains unknown. Accordingly, the physicochemical characteristics and protective effects of RT-90 on obesity were investigated in high-fat diet (HFD)-fed mice. Physicochemical property examinations showed that RT-90 consisted of small, round starch granules (D90: 20.69 ± 0.4 μm) with a crystalline structure, P-O-C stretching, and high peak melting temperature and enthalpy. Additionally, feeding mice with RT-90 significantly decreased body weight, improved oral glucose tolerance test (OGTT), reduced fatty liver and adipose tissue accumulation, lowered oxidative stress and inflammation by upregulating antioxidant enzymes (SOD, catalase, GPx) and anti-inflammatory cytokines (IL-4, IL-10), and enhanced fecal lipids and bile acid excretion. Notably, RT-90 administration in HFD-fed mice was associated with the inhibition of obesity-associated harmful bacteria ([Eubacterium]_xylanophilum group, Allobaculum, Clostridia_UCG-014, Dubosiella) and promotion of short-chain fatty acids (SCFAs)-producing gut flora, including Bifidobacterium, Lactobacillus, Bacteroides, and Parabacteroides, which suggests a possible mechanism by which RT-90 alters gut microbiota to attenuate obesity. These novel findings first revealed that RT-90 facilitates weight loss through its antioxidant, anti-inflammatory, and microbiota modulation abilities. This provides a promising strategy for managing overweight or obesity and holds potential for applications in developing healthy food products.

Flavonoid-Rich Extracts from Chuju (Asteraceae Chrysanthemum L.) Alleviate the Disturbance of Glycolipid Metabolism on Type 2 Diabetic Mice via Modulating the Gut Microbiota

Type 2 diabetes mellitus (T2DM) and its associated complications represent a significant public health issue affecting hundreds of millions of people globally; thus, measures to prevent T2DM are urgently needed. Chuju has been proven to possess antihyperglycemic activity. However, the bioactive ingredients in chuju that contribute to its antihyperglycemic activity, as well as the relationship between its antihyperglycemic activity and the gut microbiota, remain unclear. To understand the potential effects that it has on T2DM, the glycolipid metabolism and gut microbiota regulation of flavonoid-rich extracts from chuju (CJE) were investigated. The results showed that the top ten flavonoid compounds in CJE are Apigenin 6, 8-digalactoside, Apigenin 6-C-glucoside 8-C-arabinoside, Luteolin-4'-O-glucoside, Isoshaftoside, Scutellarin, Quercetin 3-O-malonylglucoside, Chrysoeriol 7-O-glucoside, Quercetin-3,4'-O-di-beta-glucoside, Luteolin 6-C-glucoside 8-C-arabinoside, and Homoorientin. Furthermore, CJE mitigated hyperglycemia and glycolipid metabolism by reducing the abundance of Faecalibaculum, Coriobacteriaceae, and Romboutsia and increasing the abundance of Alistipes. In addition, the results of Western blot analysis showed that CJE could enhance glycogen synthesis and glucose transport by up-regulating the phosphorylation of IRS1-PI3K-Akt and AMPK-GLUT4. Simultaneously, CJE could decrease gluconeogenesis by down-regulating the phosphorylation of FoxO1/GSK 3β. In conclusion, the findings of this study provide new evidence supporting the hypothesis that CJE can be used as part of a therapeutic approach for treating disturbances in glycolipid metabolism via regulating the gut microbiota and mediating the IRS1-PI3K-Akt-FoxO1/GSK 3β and AMPK-GLUT4 pathways.

New insights into microbial bile salt hydrolases: from physiological roles to potential applications

Gut microbiota has been increasingly linked to metabolic health and diseases over the past few decades. Bile acids (BAs), the major components of bile, are bidirectionally linked to intestinal microbiota, also known as the gut microbiome-BA metabolic axis. Gut microbiota-derived bile salt hydrolase (BSH, EC 3.5.1.24), which catalyzes the "gateway" reaction in a wider pathway of bile acid modification, not only shapes the bile acid landscape, but also modulates the crosstalk between gut microbiota and host health. Therefore, microbial BSHs exhibit the potential to directly or indirectly influence microbial and host physiologies, and have been increasingly considered as promising targets for the modulation of gut microbiota to benefit animal and human health. However, their physiological functions in bacterial and host physiologies are still controversial and not clear. In this review, we mainly discuss the current evidence related to the physiological roles that BSHs played in gut microbiota and human health, and the possible underlying mechanisms. Meanwhile, we also present the potential applications of BSHs and BSH-producing probiotics in various fields. Finally, we describe several important questions that need to be addressed by further investigations. A detailed exploration of the physiological significance of BSHs will contribute to their future diagnostic and therapeutic applications in improving animal and human health.

Creation of high-resistant starch rice through systematic editing of amylopectin biosynthetic genes in rs4

Resistant starch (RS) is a special kind of starch with beneficial effects on obesity, type 2 diabetes and other chronic complications. Breeding high-RS rice varieties is considered a valuable way to improve public health. However, most rice cultivars only contain an RS level lower than 2% in cooked rice, and cloning of RS genes is critical to improve RS levels in rice. The loss of function of Starch Synthases IIIa (SSIIIa) and SSIIIb, two amylopectin biosynthetic genes, could elevate RS levels up to 10%. Here, we performed a systematic genetic study of 14 amylopectin biosynthetic genes in the ssIIIa ssIIIb double mutant via genome editing, and investigated their effects on RS formation, the eating quality and grain yield. The results showed that deficiency in SSIIa, SSIVb or ISA2 under the ssIIIa ssIIIb background could each elevate RS content to above 14%, and the quadruple mutants of sbeI sbeIIb ssIIIa ssIIIb and sbeI ssIVb ssIIIa ssIIIb could further increase RS levels to over 18%. Furthermore, the eating quality of cooked rice and grain yield decreased along with the elevated RS contents, showing a trade-off among these traits. In these mutants, ssIIIa ssIIIb showed the balanced performance of RS and grain yield. This study provides insights into RS biosynthesis with a series of RS genes in the amylopectin biosynthesis pathway and practical strategy to breed high-RS rice varieties with balanced performance.

Editorial: Grappling With the Relationships of Attention-Deficit/Hyperactivity Disorder and Obesity

In this issue of the Journal, Reed and colleagues1 explore the intersection of 2 important public health problems: overweight/obesity and attention-deficit/ hyperactivity disorder (ADHD), both having a high population prevalence and tending to start in childhood. They analyzed data cross-sectionally and longitudinally from a UK birth cohort of 7,908 youth, including 442 with ADHD by either actual diagnosis or parent-rated threshold score. This epidemiologic ADHD prevalence was comparable to those in other countries, although the actual diagnosis rate was lower. They added a cross-lagged longitudinal perspective to previous reports showing a small association of obesity with ADHD, especially in adults. Their clinically important findings include the following. (1) Both disorders are associated with slightly lower birth weight, presumably reflecting a generally less favorable gestation. (2) The shift from underweight to overweight for those with ADHD occurred in preschool years, at 3 to 5 years of age. (3) ADHD symptom severity predicted overweight: for girls, "higher ADHD symptoms at ages 7, 11, and 14 predicted higher body mass index (BMI) at 11, 14, and 17, respectively." For boys, higher ADHD symptoms at age 11 predicted higher BMI at 14 years. (4) Girls had earlier onset of obesity/overweight (not necessarily a higher rate than boys with ADHD). These have numerous clinical and research implications cutting across many areas of inquiry.

Increased Crystallite Stability Enhances Gut Microbial Fermentability of Type 5 Resistant Starch

The amylolytic susceptibility of starch-lipid complexes with different forms of crystallites has been studied extensively, but the fermentation properties of these complexes remain little understood. Hence, the in vitro fecal fermentation properties of starch-lipid complexes with VI-type and VII-type crystallites were investigated in the present study. Compared to VI-type complexes, fermentation of VII-type complexes caused more severe disruption to the crystallites and resulted in greater acid, reducing sugar, and short-chain fatty acids (SCFAs) production. Moreover, fermentation of VII-type complexes promoted a greater relative abundance of SCFAs-producing bacteria in the fecal microbiota than did VI-type complexes. Our results show that the more stable VII-type complexes are utilized more effectively than VI-type complexes, which can be attributed to the bacteria binding more readily to VII-type than to VI-type complexes. Therefore, VII-type complexes were considered to deliver better health benefits than VI-type complexes due to their greater potential for producing SCFAs and stimulating beneficial gut microbial activity in the colon.

Konjac Glucomannan and Its Degradation Products Inhibit Intestinal Lipid Absorption by Regulating Gut Microbiota and the Production of Short-Chain Fatty Acids

The effect of konjac glucomannan (KGM) on lipid absorption is related to the viscosity effect and hepatic lipid synthesis. However, the molecular mechanism of regulation of intestinal lipid absorption by KGM and its correlation with gut microbiota have not been studied. This study explored the effects of KGM and degradation products of KGM (DKGM) on intestinal lipid absorption and output in obese mice and their potential mechanisms. The results showed that KGM significantly reduces blood lipids and intestinal lipid accumulation compared to DKGM in obese mice. Moreover, KGM and DKGM downregulated intestinal HDAC3 and NFLI3 expression to suppress CD36, SREBP1, FABP1, and PPARα expression. Notably, KGM more effectively inhibited fatty acid uptake in extraintestinal tissues than DKGM. Importantly, KGM more effectively enhanced the intestinal barrier, altered microbe abundance associated with lipid absorption, and promoted SCFA production than DKGM. Correlation analysis found that KGM and DKGM inhibited intestinal lipid absorption, which were positively correlated with the abundance of Lactobacillus, Desulfovibrio, Allobaculum etc. In conclusion, KGM more effectively inhibits intestinal lipid absorption and output in high-fat diet mice than DKGM, which is related to viscosity, intestinal HDAC3 activity, and differential remodeling of the microbiome. These findings provide insights into how microbe-dietary fiber interactions regulate the host energy balance.

Euglena gracilis polysaccharide modulated gut dysbiosis of obese individuals via acetic acid in an in vitro fermentation model

Gut dysbiosis is a characteristic feature of obesity and targeting gut microbiota presents a promising approach to attenuate obesity. Euglena gracilis polysaccharide (EGP) has emerged as a potential prebiotic capable of promoting health-beneficial bacteria. However, its effects on the gut dysbiosis of obese individuals remain unclear. This study investigated the impacts of EGP on gut microbiota from both non-obese and obese individuals using an in vitro fermentation model. Results showed that EGP significantly altered the gut microbiota composition and metabolism. Specifically, EGP improved the relative abundance of Paeniclostridium, Clostridium_sensu_stricto_1 and Paraclostridium of the non-obese individuals and Providencia, Enterococcus and Bacteroides of the obese individuals. Metabolomics results showed EGP significantly altered the lipid metabolism especially in the obese group with enriched bile secretion and cholesterol metabolism pathways. Noting that acetic acid was significantly increased in both groups, these acetic acid favorable microbiota from non-obese individuals was collected with acetic acid supplementation. Transplantation of these acetic acid-induced microbiota (AAiM) notably improved the richness and diversity of fecal microbiota of the obese individuals, enhancing the growth of probiotics like Bacteroides and Bifidobacterium. Consequently, AAiM significantly restructured macronutrients (including amino acids, carbohydrates and lipids) metabolism of the gut microbiota from obese individuals. Altogether, this study underscores the potential of EGP and acetic acid favorable microbiota in manipulating obesity-associated gut dysbiosis via acetic acid production.

Non-SCFA microbial metabolites associated with fiber fermentation and host health

Dietary fiber is degraded by commensal gut microbes to yield host-beneficial short-chain fatty acids (SCFAs), but personalized responses to fiber supplementation highlight a role for other microbial metabolites in shaping host health. In this review we summarize recent findings from dietary fiber intervention studies describing health impacts attributed to microbial metabolites other than SCFAs, particularly secondary bile acids (2°BAs), aromatic amino acid derivatives, neurotransmitters, and B vitamins. We also discuss shifts in microbial metabolism occurring through altered maternal dietary fiber intake and agricultural practices, which warrant further investigation. To optimize the health benefits of dietary fibers, it is essential to survey a range of metabolites and adapt recommendations on a personalized basis, according to the different functional aspects of the microbiome.

Genomic features and prevalence of Ruminococcus species in humans are associated with age, lifestyle, and disease

The genus Ruminococcus is dominant in the human gut, but higher levels of some species, such as R. gnavus, R. torques, and R. bromii, have been linked to health or disease. In this study, we analyzed >9,000 Ruminococcus metagenome-assembled genomes (MAGs) reconstructed from >5,000 subjects and revealed significant links between the prevalence of some species/subspecies and geographic origin, age, lifestyle, and disease, with subspecies prevalent in specific subpopulations showing divergent metabolic potential. Furthermore, Ruminococcus species from Lachnospiraceae encoded for carbohydrate-active enzymes (CAZy) potentially involved in the metabolism of human N- and O-glycans, whereas those from Oscillospiraceae appear to be more adapted toward fiber metabolism. These new findings contribute to elucidating the potential functional role of Ruminococcus in specific lifestyles and diseases and to decipher the diversity and the adaptation of members of this genus to the human gut.

Deleterious Effects of Yoyo Dieting and Resistant Starch on Gastrointestinal Morphology

BACKGROUND

Obesity is associated with structural deterioration in the gut. Yoyo dieting, which refers to repeated phases of dieting and non-dieting periods leading to cyclic weight loss and regain, is a common occurrence in individuals with obesity. However, there is limited evidence on how gut structures are affected in yoyo dieting. There is good evidence suggesting that increased intake of resistant starch (RS) may be beneficial in promoting structural improvements in the gut. This investigation aimed to explore the effect of yoyo dieting on gastrointestinal structure and whether RS has beneficial effects in improving obesity-related gastrointestinal damage.

METHOD

In this study, male and female C57BL/6 mice were assigned to six different diets for 20 weeks: (1) control diet, (2) high fat diet (HF), (3) yoyo diet (alternating HF and control diets every 5 weeks), (4) control diet with RS, (5) HF with RS, and (6) yoyo diet with RS. Distal colon was collected for epithelial barrier integrity measurement. The small and large intestines were collected for histological assessment.

RESULTS

After 20 weeks, yoyo dieting resulted in increased colonic inflammation and exacerbated mucosal damage in comparison with continuous HF diet feeding. RS supplemented in HF and yoyo diets reduced mucosal damage in comparison to diets without RS. However, RS supplementation in a control diet significantly increased inflammation, crypt length, and goblet cell density. There were no significant differences in epithelial change and epithelial barrier integrity across diet groups.

CONCLUSIONS

This study suggests that yoyo dieting worsens gut damage, and incorporating high levels of RS may be detrimental in the absence of dietary challenge.

Synergistic Interplay of Diet, Gut Microbiota, and Insulin Resistance: Unraveling the Molecular Nexus

This comprehensive review explores the intricate relationship between gut microbiota, diet, and insulin resistance, emphasizing the novel roles of diet-induced microbial changes in influencing metabolic health. It highlights how diet significantly influences gut microbiota composition, with different dietary patterns fostering diverse microbial communities. These diet-induced changes in the microbiome impact human metabolism by affecting inflammation, energy balance, and insulin sensitivity, particularly through microbial metabolites like short-chain fatty acids (SCFAs). Focusing the key mediators like endotoxemia and systemic inflammation, and introduces personalized microbiome-based therapeutic strategies, it also investigates the effects of dietary components-fiber, polyphenols, and lipids-on microbiota and insulin sensitivity, along with the roles of protein intake and amino acid metabolism. The study compares the effects of Western and Mediterranean diets on the microbiota-insulin resistance axis. Therapeutic implications, including probiotics, fecal microbiota transplantation (FMT), and personalized diets, are discussed. Key findings reveal that high-fat diets, especially those rich in saturated fats, contribute to dysbiosis and increased intestinal permeability, while high-fiber diets promote beneficial bacteria and SCFAs. The review underscores the future potential of food and microbiota interventions for preventing or managing insulin resistance.

Preparation of debranched starch with high thermal stability and crystallinity using a novel thermal cycling treatment

Herein, the effects of temperature cycling (4 °C/50 °C/100 °C) on the recrystallization, physicochemical properties, and digestibility of debranched starch (DBS) were investigated. Temperature cycling involved heating DBS to 100 °C to dissociate weak heat-sensitive crystalline structures and cooling to 4 °C to induce the rapid growth of crystal nuclei, followed by maintaining the temperature at 50 °C to promote orderly crystalline growth. This procedure aimed to increase the degree of crystalline structure in recrystallized DBS, thereby resulting in DBS that was heat- and digestion-resistant. Temperature cycling increased the dissociation temperature of DBS, and temperatures of up to 114.8 °C were attained after five cycling times. With increasing cycles, the crystalline structure of DBS transitioned from B-type to the more robust and compact A-type, and the crystallinity increased to ∼81.9 % (after seven cycles). Raman and Fourier transform infrared (FTIR) spectra indicated that temperature cycling enhanced the short-range ordered structure of DBS. Moreover, in vitro digestion experiments demonstrated that the resistant starch content of DBS increased to ∼61.9 % after eight cycles. To summarize, this study demonstrated a green and effective method for preparing heat-and digestion-resistant recrystallized DBS, which can be used for developing dietary supplements and low gastrointestinal staples.

The Interactions Between Diet and Gut Microbiota in Preventing Gestational Diabetes Mellitus: A Narrative Review

Recent studies have revealed that dysbiosis, defined as alterations in gut microbiota, plays an important role in the development and the progression of many non-communicable diseases, including metabolic disorders, such as type 2 diabetes mellitus and gestational diabetes mellitus (GDM). The high frequency of GDM makes this disorder an important public health issue, which needs to be addressed in order to reduce both the maternal and fetal complications that are frequently associated with this disease. The studies regarding the connections between gut dysbiosis and GDM are still in their early days, with new research continuously emerging. This narrative review seeks to outline the mechanisms through which a healthy diet that protects the gut microbiota is able to prevent the occurrence of GDM, thus providing medical nutritional therapeutic perspectives for the management of GDM.

Control of Starch Molecular Weight by Enzyme Treatment Facilitates the Formation of V-Type Starch-Resveratrol Complexes in a High-Pressure Homogenization Environment and Their Modulation Effects on the Gut Microbiota

As the concept of precision nutrition has been gradually popularized in recent years, the relationship between the structure of starch-polyphenol complexes with significant health effects and their nutritional functions has been progressively investigated. In this study, G50 high-amylose maize starch with different molecular weights was first prepared by pullulanase and α-amylase, and their effects on the structural formation, digestion properties, and release behaviors of the starch-resveratrol (RA) complex were discussed. The results confirmed that enzyme-treated starch could enhance intermolecular hydrogen bonding and hydrophobic interactions between starch and RA in a high-pressure homogeneous (HPH) environment, forming stable single-helix and V-type crystalline structures while reducing the B-type crystalline structures. Meanwhile, the in vitro experiment showed that when the RA addition was 3%, the resistant starch content of the starch-RA complex could reach 60.3%, and its RA colonic transport rate could reach more than 97%. Interestingly, the starch-RA complex with a relatively higher V-type crystalline structure content contributed to the production of short-chain fatty acids (SCFAs), especially butyrate, and it might be effective in carbohydrate metabolism and immunometabolism by promoting the functions of Phascolarctobacteriu and Alistipes. These findings provide new ideas for the design of the nutritional functions of RS.

Diagnosing and engineering gut microbiomes

The microbes, nutrients and toxins that we are exposed to can have a profound effect on the composition and function of the gut microbiome. Thousands of peer-reviewed publications link microbiome composition and function to health from the moment of birth, right through to centenarians, generating a tantalizing glimpse of what might be possible if we could intervene rationally. Nevertheless, there remain relatively few real-world examples where successful microbiome engineering leads to beneficial health effects. Here we aim to provide a framework for the progress needed to turn gut microbiome engineering from a trial-and-error approach to a rational medical intervention. The workflow starts with truly understanding and accurately diagnosing the problems that we are trying to fix, before moving on to developing technologies that can achieve the desired changes.

Dietary starch structure modulates nitrogen metabolism in laying hens via modifying glucose release rate

The objective of this study was to investigate the effects of starch structure (Amylopectin/Amylose, AP/AM) in a low-protein diet on production performance, nitrogen utilization efficiency, and cecal flora in laying hens. Four hundred eighty 45-wk-age Hy-Line Gray laying hens were randomly allocated to five dietary groups and subjected to a 12-wk feeding trial. The AP/AM ratios of the five experiment diets were 1.0, 1.5, 2.0, 3.0, and 4.0. The results indicated that compared to other groups, laying hens fed with AP/AM 4.0 diets showed significantly improved average egg weight and feed conversion ratio (P < 0.05). Furthermore, as the AP/AM ratio increased, there was a significant linear enhancement in intestinal amino acids apparent digestibility, apparent metabolizable energy, and villus area (P < 0.05). Compared to the high AP groups, high-AM diets significantly increased eggshell thickness, crude protein digestibility, and reduced energy supply from amino acid oxidation in ileum (P < 0.05). Additionally, moderate-AM diets enriched with short-chain fatty acid-producing bacteria in the cecum, such as Lactobacillus, Rikenellaceae_RC9_gut_group, and Christensenellaceae_R-7_group, which are associated with the promoting nitrogen utilization. These findings may offer useful information on optimizing starch structure for the design of food products and relevant therapies due to the potential effects on nutrient metabolism and gut homeostasis.

Exploring the Gut Microbiota: Key Insights Into Its Role in Obesity, Metabolic Syndrome, and Type 2 Diabetes

The gut microbiota (GM), comprising trillions of microorganisms in the gastrointestinal tract, is a key player in the development of obesity and related metabolic disorders, such as type 2 diabetes (T2D), metabolic syndrome (MS), and cardiovascular diseases. This mini-review delves into the intricate roles and mechanisms of the GM in these conditions, offering insights into potential therapeutic strategies targeting the microbiota. The review elucidates the diversity and development of the human GM, highlighting its pivotal functions in host physiology, including nutrient absorption, immune regulation, and energy metabolism. Studies show that GM dysbiosis is linked to increased energy extraction, altered metabolic pathways, and inflammation, contributing to obesity, MS, and T2D. The interplay between dietary habits and GM composition is explored, underscoring the influence of diet on microbial diversity and metabolic functions. Additionally, the review addresses the impact of common medications and therapeutic interventions like fecal microbiota transplantation on GM composition. The evidence so far advocates for further research to delineate the therapeutic potential of GM modulation in mitigating obesity and metabolic diseases, emphasizing the necessity of clinical trials to establish effective and sustainable treatment protocols.

Improving the growth and intestinal colonization of Escherichia coli Nissle 1917 by strengthening its oligopeptides importation ability

Escherichia coli Nissle 1917 (EcN), the probiotic featured with well-established safety in different host, is emerging as a favored chassis for the construction of engineered probiotics for disease treatment. However, limited by the low intestinal colonization ability of EcN, repeated administration is required to maximize the health benefits of the EcN-derived engineered probiotics. Here, using fecal metabolites as "metabolites pool", we developed a metabolomic strategy to characterize the comprehensive metabolic profile of EcN. Compared with Prevotella copri DSM 18205 (P. copri), one of the dominant microbes in gut flora, EcN exhibited minor growth advantage under the fecal metabolites-containing condition for its lower metabolic capability towards fecal metabolites. Further study indicated that EcN lacked the ability to import the oligopeptides containing more than two amino acids. The shortage of oligopeptides-derived amino acids might limit the growth of EcN by restricting its purine metabolism. Assisted with the bioinformatic and qRT-PCR analyses, we identified a tripeptides-specific importer Pc-OPT in P. copri, which was mainly distributed in genera Prevotella and Bacteroides. Overexpression of Pc-OPT improved the tripeptides importation of EcN and promoted its growth and intestinal colonization. Notably, 16S rRNA gene amplicon sequencing results indicated that strengthening the oligopeptides importation ability of EcN might promote its intestinal colonization by adjusting the gut microbial composition. Our study reveals that the growth and intestinal colonization of EcN is limited by its insufficient oligopeptides importation and paves road for promoting the efficacy of the EcN-derived synthetic probiotics by improving their intestinal colonization ability.

Resistant Potato Starch Supplementation Reduces Serum Free Fatty Acid Levels and Influences Bile Acid Metabolism

Background: Resistant starches, such as high-amylose maize starch and resistant potato starch (RPS), have prebiotic effects that are linked to improved metabolism at >15 g/day, but the effects at lower doses have not been reported. Methods: We performed an exploratory post hoc analysis of free fatty acids (FFAs), bile acids (BAs), and ketone bodies in serum previously collected from a randomized, double-blind, placebo-controlled clinical trial evaluating the effects of one- and four-week consumption of 3.5 g/day RPS versus a placebo using two-way ANOVA adjusted by pFDR. Associations between week 4 changes in FFAs, BAs, and ketone bodies were assessed by Pearson's correlations. Results: RPS consumption reduced total FFAs relative to the placebo, including multiple unsaturated FFAs and octanedioic acid, with reductions in taurine- and glycine-conjugated secondary BAs also detected (q < 0.05). No changes in ketone bodies were observed (q > 0.05). Changes in 7-ketodeoxycholic acid (r = -0.595) and glycolithocholic acid (r = -0.471) were inversely correlated with treatment-induced reductions in FFAs for RPS but not the placebo, suggesting the effects were from the prebiotic. Shifts in β-hydroxybutyrate were further correlated with FFA changes in both treatments (q < 0.05). Conclusions: These findings demonstrate that low doses of RPS positively influence fatty acid metabolism in humans, reducing circulating levels of FFA and conjugated BAs.

An insoluble cellulose nanofiber with robust expansion capacity protects against obesity

An imbalance between energy intake and energy expenditure predisposes obesity and its related metabolic diseases. Soluble dietary fiber has been shown to improve metabolic homeostasis mainly via microbiota reshaping. However, the application and metabolic effects of insoluble fiber are less understood. Herein, we employed nanotechnology to design citric acid-crosslinked carboxymethyl cellulose nanofibers (CL-CNF) with a robust capacity of expansion upon swelling. Supplementation with CL-CNF reduced food intake and delayed digestion rate in mice by occupying stomach. Besides, CL-CNF treatment mitigated diet-induced obesity and insulin resistance in mice with enhanced energy expenditure, as well as ameliorated inflammation in adipose tissue, intestine and liver and reduced hepatic steatosis, without any discernible signs of toxicity. Additionally, CL-CNF supplementation resulted in enrichment of probiotics such as Bifidobacterium and decreased in the relative abundances of deleterious microbiota expressing bile salt hydrolase, which led to increased levels of conjugated bile acids and inhibited intestinal FXR signaling to stimulate the release of GLP-1. Taken together, our findings demonstrate that CL-CNF administration protects mice from diet-induced obesity and metabolic dysfunction by reducing food intake, enhancing energy expenditure and remodeling gut microbiota, making it a potential therapeutic strategy against metabolic diseases.

Resistant starch reduces glycolysis by HK2 and suppresses high-fructose corn syrup-induced colon tumorigenesis

BACKGROUND

The intake of high-fructose corn syrup (HFCS) may increase the risk of colorectal cancer (CRC). This study aimed to explore the potential effects and mechanisms of resistant starch (RS) in HFCS-induced colon tumorigenesis.

METHODS

The azoxymethane/dextran sodium sulfate (AOM/DSS) and ApcMin/+ mice models were used to investigate the roles of HFCS and RS in CRC in vivo. An immunohistochemistry (IHC) staining analysis was used to detect the expression of proliferation-related proteins in tissues. 16S rRNA sequencing for microbial community, gas chromatography for short-chain fatty acids (SCFAs), and mass spectrometry analysis for glycolysis products in the intestines were performed. Furthermore, lactic acid assay kit was used to detect the glycolysis levels in vitro.

RESULTS

RS suppressed HFCS-induced colon tumorigenesis through reshaping the microbial community. Mechanistically, the alteration of the microbial community after RS supplement increased the levels of intestinal SCFAs, especially butyrate, leading to the suppression of glycolysis and CRC cell proliferation by downregulating HK2.

CONCLUSIONS

Our study identified RS as a candidate of protective factors in CRC and may provide a potential target for HFCS-related CRC treatment.

Bacteroides uniformis degrades β-glucan to promote Lactobacillus johnsonii improving indole-3-lactic acid levels in alleviating colitis

BACKGROUND

Intake of dietary fiber is associated with a reduced risk of inflammatory bowel disease. β-Glucan (BG), a bioactive dietary fiber, has potential health-promoting effects on intestinal functions; however, the underlying mechanism remains unclear. Here, we explore the role of BG in ameliorating colitis by modulating key bacteria and metabolites, confirmed by multiple validation experiments and loss-of-function studies, and reveal a novel bacterial cross-feeding interaction.

RESULTS

BG intervention ameliorates colitis and reverses Lactobacillus reduction in colitic mice, and Lactobacillus abundance was significantly negatively correlated with the severity of colitis. It was confirmed by further studies that Lactobacillus johnsonii was the most significantly enriched Lactobacillus spp. Multi-omics analysis revealed that L. johnsonii produced abundant indole-3-lactic acid (ILA) leading to the activation of aryl hydrocarbon receptor (AhR) responsible for the mitigation of colitis. Interestingly, L. johnsonii cannot utilize BG but requires a cross-feeding with Bacteroides uniformis, which degrades BG and produces nicotinamide (NAM) to promote the growth of L. johnsonii. A proof-of-concept study confirmed that BG increases L. johnsonii and B. uniformis abundance and ILA levels in healthy individuals.

CONCLUSIONS

These findings demonstrate the mechanism by which BG ameliorates colitis via L. johnsonii-ILA-AhR axis and reveal the important cross-feeding interaction between L. johnsonii and B. uniformis. Video Abstract.

The Impact of Yoyo Dieting and Resistant Starch on Weight Loss and Gut Microbiome in C57Bl/6 Mice

Cyclic weight loss and subsequent regain after dieting and non-dieting periods, a phenomenon termed yoyo dieting, places individuals at greater risk of metabolic complications and alters gut microbiome composition. Resistant starch (RS) improves gut health and systemic metabolism. This study aimed to investigate the effect of yoyo dieting and RS on the metabolism and gut microbiome. C57BL/6 mice were assigned to 6 diets for 20 weeks, including control, high fat (HF), yoyo (alternating HF and control diets every 5 weeks), control with RS, HF with RS, and yoyo with RS. Metabolic outcomes and microbiota profiling using 16S rRNA sequencing were examined. Yoyo dieting resulted in short-term weight loss, which led to improved liver health and insulin tolerance but also a greater rate of weight gain compared to continuous HF feeding, as well as a different microbiota profile that was in an intermediate configuration between the control and HF states. Mice fed HF and yoyo diets supplemented with RS gained less weight than those fed without RS. RS supplementation in yoyo mice appeared to shift the gut microbiota composition closer to the control state. In conclusion, yoyo dieting leads to obesity relapse, and increased RS intake reduces weight gain and might help prevent rapid weight regain via gut microbiome restoration.

The complex link between the gut microbiome and obesity-associated metabolic disorders: Mechanisms and therapeutic opportunities

Microbial interactions are widespread and important processes that support the link between disease and microbial ecology. The gut microbiota is a major source of microbial stimuli that can have detrimental or beneficial effects on human health. It is also an endocrine organ that maintains energy homeostasis and host immunity. Obesity is a highly and increasingly prevalent metabolic disease and the leading cause of preventable death worldwide. An imbalance in the gut microbiome is associated with several diseases including obesity-related metabolic disorders. This review summarizes the complex association between the gut microbiome and obesity-associated metabolic diseases and validates the role and mechanisms of ecological dysregulation in the gut in obesity-associated metabolic disorders. Therapies that could potentially alleviate obesity-associated metabolic diseases by modulating the gut microbiota are discussed.

Mutations in starch BRANCHING ENZYME 2a suppress the traits caused by the loss of ISOAMYLASE1 in barley

KEY MESSAGE

The hvbe2a mutations restore the starch-deficient phenotype caused by the hvisa1 and hvflo6 mutations in barley endosperm. The genetic interactions among starch biosynthesis genes can be exploited to alter starch properties, but they remain poorly understood due to the various combinations of mutations to be tested. Here, we isolated two novel barley mutants defective in starch BRANCHING ENZYME 2a (hvbe2a-1 and hvbe2a-2) based on the starch granule (SG) morphology. Both hvbe2a mutants showed elongated SGs in the endosperm and increased resistant starch content. hvbe2a-1 had a base change in HvBE2a gene, substituting the amino acid essential for its enzyme activity, while hvbe2a-2 is completely missing HvBE2a due to a chromosomal deletion. Further genetic crosses with barley isoamylase1 mutants (hvisa1) revealed that both hvbe2a mutations could suppress defects in endosperm caused by hvisa1, such as reduction in starch, increase in phytoglycogen, and changes in the glucan chain length distribution. Remarkably, hvbe2a mutations also transformed the endosperm SG morphology from the compound SG caused by hvisa1 to bimodal simple SGs, resembling that of wild-type barley. The suppressive impact was in competition with floury endosperm 6 mutation (hvflo6), which could enhance the phenotype of hvisa1 in the endosperm. In contrast, the compound SG formation induced by the hvflo6 hvisa1 mutation in pollen was not suppressed by hvbe2a mutations. Our findings provide new insights into genetic interactions in the starch biosynthetic pathway, demonstrating how specific genetic alterations can influence starch properties and SG morphology, with potential applications in cereal breeding for desired starch properties.

Recent Advances in Physical Processing Techniques to Enhance the Resistant Starch Content in Foods: A Review

The physical modification of starch to produce resistant starch (RS) is a viable strategy for the glycemic index (GI) lowering of foods and functionality improvement in starchy food products. RS cannot be digested in the small intestine but can be fermented in the colon to produce short-chain fatty acids rather than being broken down by human digestive enzymes into glucose. This provides major health advantages, like better blood sugar regulation, weight control, and a lower chance of chronic illnesses. This article provides a concise review of the recent developments in physical starch modification techniques, including annealing, extrusion, high-pressure processing, radiation, and heat-moisture treatment. Specifically, the focus of this paper is on the alteration of the crystalline structure of starch caused by the heat-moisture treatment and annealing and its impact on the resistance of starch to enzymatic hydrolysis, as well as the granular structure and molecular arrangement of starch caused by extrusion and high-pressure processing, and the depolymerization and crosslinking that results from radiation. The impacts of these alterations on starch's textural qualities, stability, and shelf life are also examined. This review demonstrates how physically modified resistant starch can be used as a flexible food ingredient with both functional and health benefits. These methods are economically and ecologically sustainable since they successfully raise the RS content and improve its functional characteristics without the need for chemical reagents. The thorough analysis of these methods and how they affect the structural characteristics and health advantages of RS emphasizes the material's potential as an essential component in the creation of functional foods that satisfy contemporary dietary and health requirements.

High-Resistant Starch Based on Amylopectin Cluster via Extrusion: From the Perspective of Chain-Length Distribution and Structural Formation

Resistant starch (RS) has the advantage of reshaping gut microbiota for human metabolism and health, like glycemic control, weight loss, etc. Among them, RS3 prepared from pure starch is green and safe, but it is hard to achieve structural control. Here, we regulate the crystal structure of starch with different chain-length distributions (CLDs) via extrusion at low/high shearing levels. The change in CLDs in extruded starch was obtained, and their effects on the fine structure (Dm, dBragg, dLorentz, degree of order and double helix, degree of crystal) of RS and its physicochemical properties were investigated by SAXS, FTIR, XRD and 13C NMR analyses. The results showed that the RS content under a 250 r/min extrusion condition was the highest at 61.52%. Furthermore, the crystalline system induced by high amylopectin (amylose ≤ 4.78%) and a small amount of amylose (amylose ≥ 27.97%) was favorable for obtaining a high content of RS3-modified products under the extruding environment. The control of the moderate proportion of the A chains (DP 6-12) in the starch matrix was beneficial to the formation of RS.

[Nutrition, metabolism, brain and mental health]

This review article explores the intricate relationship between nutrition, metabolism, brain function and mental health. It highlights two key complementary models: the energy balance model and the more comprehensive carbohydrate-insulin model, to understand the development of obesity and metabolic dysfunctions. It particularly focuses on the role of dopamine in dietary regulation and insulin in the brain, both of which are crucial in the pathogenesis of neurodegenerative and stress-associated mental disorders. Additionally, the significance of sleep and dietary habits, such as medically assisted calorie restriction for mental health and the concept of "brain food" are described. These findings emphasize the importance of nutritional medicine in psychiatry and psychotherapy and the consideration of metabolic states for the prevention and treatment of mental and neurodegenerative diseases.

Ketogenic diet-induced bile acids protect against obesity through reduced calorie absorption

The low-carbohydrate ketogenic diet (KD) has long been practiced for weight loss, but the underlying mechanisms remain elusive. Gut microbiota and metabolites have been suggested to mediate the metabolic changes caused by KD consumption, although the particular gut microbes or metabolites involved are unclear. Here, we show that KD consumption enhances serum levels of taurodeoxycholic acid (TDCA) and tauroursodeoxycholic acid (TUDCA) in mice to decrease body weight and fasting glucose levels. Mechanistically, KD feeding decreases the abundance of a bile salt hydrolase (BSH)-coding gut bacterium, Lactobacillus murinus ASF361. The reduction of L. murinus ASF361 or inhibition of BSH activity increases the circulating levels of TDCA and TUDCA, thereby reducing energy absorption by inhibiting intestinal carbonic anhydrase 1 expression, which leads to weight loss. TDCA and TUDCA treatments have been found to protect against obesity and its complications in multiple mouse models. Additionally, the associations among the abovementioned bile acids, microbial BSH and metabolic traits were consistently observed both in an observational study of healthy human participants (n = 416) and in a low-carbohydrate KD interventional study of participants who were either overweight or with obesity (n = 25). In summary, we uncover a unique host-gut microbiota metabolic interaction mechanism for KD consumption to decrease body weight and fasting glucose levels. Our findings support TDCA and TUDCA as two promising drug candidates for obesity and its complications in addition to a KD.