Antiobesity effect of healthy food crops and functional foods: A systematic review of their mechanisms

Diet is a modifiable risk factor in the prevention and management of obesity, and various foods have the potential to aid in obesity management by modulating different pathways involved in the disease's pathology. We performed a systematic review of literature, using CINAHL, PubMed, and Google Scholar, focusing on the antiobesity potential of foods crops and functional food products, and their mechanisms of action and clinical evidence. Sixty-four articles were identified, of which 41 investigated food crops, while 23 investigated functional products. Food crops, such as cereals, vegetables, fruits, mushrooms, seaweeds, legumes, herbs, spices, and cocoa seeds, have antiobesity effects through mechanisms such as altering the metabolism of glucolipids by inhibiting enzymes like α-amylase and α-glucosidase, stimulating the bioenergetics of thermogenic fat, modulating gut microbiota, and inhibiting lipogenesis and storage. In addition, developed functional teas, beverages, and yoghurt have antiobesity effects through similar or different mechanisms, such as enhancing energy expenditure and satiety, suppressing adipogenesis and lipolysis, improving glucose and lipid metabolism, and altering hormonal secretion. This review reemphasized the significance of food in the control of obesity, and highlights the distinct methods these explored foods exert their antiobesity effects. In conclusion, foods are safe and effective means of combating obesity without the side effects of conventional drugs, which can help inform dietary choices, assist professionals in providing more accurate advice, and also lead to better understanding of food and its effect on overall health of the public. This approach will eradicate global diseases, especially if more underutilized and indigenous food crops are extensively researched.

The Effect of Dietary Oat Consumption and Its Constituents on Fat Storage and Obesity

This review is to summarize and analyze the currently available knowledge concerning the action of oat (Avena sativa L.) consumption on obesity, as well as possible constituents and extra- and intracellular mediators responsible for its anti-obesity effect. The oat constituents could reduce fat storage via several mediatory mechanisms - brain centers regulating appetite, gastrointestinal functions, gut bacteria, fat synthesis and metabolism and maybe via changes in oxidative processes, steroid hormones receptors and adipose tissue vascularization. Several oat constituents (starch, fiber and beta-glucan) could have anti-obesity properties, whilst one oat constituent (starch or fiber) could affect fat storage via several mechanisms of action.

Butyl Group Distribution, Intestinal Digestion, and Colonic Fermentation Characteristics of Different Butyrylated Starches

Despite being a promising butyrate carrier, butyrylated starch remains poorly understood in terms of the correlation between starch structure and fermentation characteristics. Herein, three butyrylated starches derived from different botanical sources were prepared with a similar degree of substitution. Raman microscopy and water contact angle analysis suggested that a relatively large proportion of butyl group substitutions occurred within the interior of butyrylated waxy maize starch (B-WMS) granules. In vitro digestion results showed that branch points provided butyl groups with a specific protection from enzymatic hydrolysis, whereas butyl groups significantly increased the resistant starch content of butyrylated starch. Moreover, the porous morphology with less distributed butyl groups on the granular surface contributed to a faster fermentation rate in B-WMS. The current study reveals the influence of botanical origin on butyl group distribution, which in turn plays a pivotal role in regulating the intestinal digestion and colonic fermentation of butyrylated starch.

AgRP/NPY and POMC neurons in the arcuate nucleus and their potential role in treatment of obesity

Obesity is a major health crisis affecting over a third of the global population. This multifactorial disease is regulated via interoceptive neural circuits in the brain, whose alteration results in excessive body weight. Certain central neuronal populations in the brain are recognised as crucial nodes in energy homeostasis; in particular, the hypothalamic arcuate nucleus (ARC) region contains two peptide microcircuits that control energy balance with antagonistic functions: agouti-related peptide/neuropeptide-Y (AgRP/NPY) signals hunger and stimulates food intake; and pro-opiomelanocortin (POMC) signals satiety and reduces food intake. These neuronal peptides levels react to energy status and integrate signals from peripheral ghrelin, leptin, and insulin to regulate feeding and energy expenditure. To manage obesity comprehensively, it is crucial to understand cellular and molecular mechanisms of information processing in ARC neurons, since these regulate energy homeostasis. Importantly, a specific strategy focusing on ARC circuits needs to be devised to assist in treating obese patients and maintaining weight loss with minimal or no side effects. The aim of this review is to elucidate the recent developments in the study of AgRP-, NPY- and POMC-producing neurons, specific to their role in controlling metabolism. The impact of ghrelin, leptin, and insulin signalling via action of these neurons is also surveyed, since they also impact energy balance through this route. Lastly, we present key proteins, targeted genes, compounds, drugs, and therapies that actively work via these neurons and could potentially be used as therapeutic targets for treating obesity conditions.

The impact of the physical form of torularhodin on its metabolic fate in the gastrointestinal tract

Torularhodin is a fungal carotenoid with multiple health benefits. However, the relationship between its physical form and metabolic fate in the gastrointestinal tract (GIT), which is essential to its bioavailability and health efficacy, has rarely been studied. Thus, physical forms of torularhodin including nanoemulsion powder (T-EP), capsules of the T-EP by alginate (T-EPA), and solution in MCT oil (T-oil) were used in the study. T-EP was produced through OSA-starch-mediated torularhodin emulsification and spray drying whereas the T-EPA was alginate-based capsules of the T-EP particles that were entrapped in the network structure of the alginate matrix as observed by scanning electron microscopy (SEM). The oil digestibility in the simulated small intestine was decreased from T-EP (100%), T-oil (60%) to T-EPA (40%), and the bioaccessibilities were 27%, 15% and 12%, respectively. The in vivo study using mice revealed that the content of torularhodin gradually decreased along with the digestion time in both the stomach and small intestine while a significantly higher colonic accumulation was observed in T-EPA compared to T-oil and T-EP. In vitro fecal fermentation showed that propionate (32 mM) was the predominant metabolite produced by torularhodin in the physical form of T-EPA. Thus, the physical form of torularhodin is a significant contributing factor to its GIT metabolic fate, and a health outcome-oriented design of the physical form of torularhodin or other nutraceuticals is beneficial for the development of functional foods with enhanced health benefits.

Slow digestion-oriented dietary strategy to sustain the secretion of GLP-1 for improved glucose homeostasis

Dysregulated glucose metabolism is associated with many chronic diseases such as obesity and type 2 diabetes mellitus (T2DM), and strategies to restore and maintain glucose homeostasis are essential to health. The incretin hormone of glucagon-like peptide-1 (GLP-1) is known to play a critical role in regulating glucose homeostasis and dietary nutrients are the primary stimuli to the release of intestinal GLP-1. However, the GLP-1 producing enteroendocrine L-cells are mainly distributed in the distal region of the gastrointestinal tract where there are almost no nutrients to stimulate the secretion of GLP-1 under normal situations. Thus, a dietary strategy to sustain the release of GLP-1 was proposed, and the slow digestion property and dipeptidyl peptidase IV (DPP-IV) inhibitory activity of food components, approaches to reduce the rate of food digestion, and mechanisms to sustain the release of GLP-1 were reviewed. A slow digestion-oriented dietary approach through encapsulation of nutrients, incorporation of viscous dietary fibers, and enzyme inhibitors of phytochemicals in a designed whole food matrix will be implemented to efficiently reduce the digestion rate of food nutrients, potentiate their distal deposition and a sustained secretion of GLP-1, which will be beneficial to improved glucose homeostasis and health.

Cross-linked arabinoxylan in a Ca2+-alginate matrix reversed the body weight gain of HFD-fed C57BL/6J mice through modulation of the gut microbiome

Here, we compared the effects of different physical forms of arabinoxylan (AX) - a microsphere of cross-linked arabinoxylan (CAX) in a Ca²⁺-alginate matrix (MC) and physical mixture of AX and alginate (PM) on gut microbiota and development of obesity in C57BL/6J mice. Supplementation of MC in high fat (HF) diet to mice for 10 weeks significantly reversed the body weight gain induced by the HF diet, along with less fat accumulation in both livers and the epididymal adipose than the PM group. Microbiome analysis showed that MC significantly altered the gut microbiota composition with a noticeable increase of butyrogenic bacteria of Lachnospiraceae. The butyrate produced by MC fermentation and the increased abundance of Lachnospiraceae might be the underlying mechanism of the anti-obesity effect of MC. The results indicated that the physical forms of dietary fiber are closely associated with its health benefits, and MC might be served as a new functional food ingredient to prevent obesity.

Dietary Methionine Restriction Ameliorated Fat Accumulation, Systemic Inflammation, and Increased Energy Metabolism by Altering Gut Microbiota in Middle-Aged Mice Administered Different Fat Diets

Diet greatly influences gut microbiota. Dietary methionine restriction (MR) prevents and ameliorates age-related or high-fat-induced diseases and prolongs life span. This study aimed to reveal the impact of MR on gut microbiota in middle-aged mice with low-, medium-, high-fat diets. C57BL/6J mice were randomly divided into six groups with different MR and fat-content diets. Multiple indicators of intestinal function, fat accumulation, energy consumption, and inflammation were measured. 16S rRNA gene sequencing was used to analyze cecal microbiota. Our results indicated that MR considerably reduced the concentrations of lipopolysaccharide (LPS) and increased short-chain fatty acids (SCFAs) by upregulating the abundance of Corynebacterium and SCFA-producing bacteria Bacteroides, Faecalibaculum, and Roseburia and downregulating the LPS-producing or proinflammatory bacteria Desulfovibrio and Escherichia-Shigella. The effect of MR on LPS and SCFAs further reduced fat accumulation and systemic inflammation, enhanced heat production, and mediated the LPS/LBP/CD14/ TLR4 pathway to strength the intestinal mucosal immunity barrier in middle-aged mice.

Antiobesity Effect of Flaxseed Polysaccharide via Inducing Satiety due to Leptin Resistance Removal and Promoting Lipid Metabolism through the AMP-Activated Protein Kinase (AMPK) Signaling Pathway

Obesity is a metabolic syndrome worldwide that causes many chronic diseases. Recently, we found an antiobesity effect of flaxseed polysaccharide (FP), but the mechanism remains to be elucidated. In this study, rats were first induced to develop obesity by being fed a high-fat diet. The obese rats were then fed a control diet, AIN-93M (group HFD), or a 10% FP diet (group FPD). The body weight, body fat, adipose tissue and liver sections, serous total triglycerides, levels of fasting blood glucose in serum, serous insulin, inflammatory cytokines in serum, and serous proteins within the leptin-neuropeptide Y (NPY) and AMP-activated protein kinase (AMPK) signaling pathway were determined and analyzed. FP intervention significantly reduced body weight and abdominal fat from 530 ± 16 g and 2.15% ± 0.30% in group HFD to 478 ± 10 g and 1.38% ± 0.48% in group FPD, respectively. This effect was achieved by removing leptin resistance possibly by inhibiting inflammation and recovering satiety through the significant downregulation of NPY and the upregulation of glucagon-like peptide 1. Adiponectin was then significantly upregulated probably via the gut-brain axis and further activated the AMPK signaling pathway to improve lipid metabolism including the improvement of lipolysis and fatty acid oxidation and the suppression of lipogenesis. This is the first report of the proposed antiobesity mechanism of FP, thereby providing a comprehensive understanding of nonstarch polysaccharides and obesity.

Are Nonnutritive Sweeteners Obesogenic? Associations between Diet, Faecal Microbiota, and Short-Chain Fatty Acids in Morbidly Obese Subjects

Obesity has been associated with changes in the gut microbiota and its metabolites. The study explored changes in the faecal microbiota and short-chain fatty acids (SCFA) associated with the diet (including nonnutritive sweeteners (NNSs)) and evaluated metabolic consequences in subjects with morbid obesity. The diet was assessed with a validated food frequency questionnaire. One unit of NNSs was 100 mL beverage with NNSs or 2 tablets/teaspoons of NNSs. The faecal microbiota was assessed with GA-map® dysbiosis test and SCFA with gas chromatography and flame ionisation detection. Fourteen men and 75 women with a mean age of 44.6 (SD 8.7) years, BMI 41.8 (SD 3.6) kg/m², and intake of NNSs 7.5 units/day (SD 3.2; range 0-43) were included. Faecal butyric acid was positively and negatively associated with the intake of starch (partial correlation = 0.264; p=0.015) and NNSs (partial correlation = -0.274; p=0.011), respectively. NNSs were associated with changes in four out of 39 bacterial groups. Butyric acid has antiobesogenic effects, reduces insulin resistance, and improves dyslipidaemia. Since the weight-reducing effect of NNSs on obese adults trying to lose weight is dubious, it seems imprudent to use NNSs that might counteract the favourable effects of butyric acid.

Starch and β-glucan in a whole-grain-like structural form improve hepatic insulin sensitivity in diet-induced obese mice

WGLSF improves hepatic insulin resistance and glucose homeostasis in diet-induced obese mice.