The multifactorial interplay of diet, the microbiome and appetite control: current knowledge and future challenges

Association of the gut microbiota with clinical variables in obese and lean Emirati subjects

Background

Growing evidence supports the role of gut microbiota in obesity, yet exact associations remain largely unknown. Specifically, very little is known about this association in the Emirati population.

Methods

We explored differences in gut microbiota composition, particularly the Firmicutes/Bacteroidetes (F/B) ratio, between 43 obese and 31 lean adult Emirate counterparts, and its association with obesity markers, by using V3-V4 regions of 16 S ribosomal RNA gene sequencing data. Furthermore, we collected anthropometric and biochemical data.

Results

The two major phyla in obese and lean groups were Firmicutes and Bacteroidetes. We observed a significantly lower alpha diversity (Shannon index) in obese subjects and a significant difference in beta diversity and phylum and genus levels between the two groups. The obese group had higher abundances of Verrucomicrobia and Saccharibacteira and lower abundances of Lentisphaerae. Acidaminococcus and Lachnospira were more abundant in obese subjects and positively correlated with adiposity markers. No correlations were found between the gut microbiota and biochemical variables, such as fasting blood sugar, total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides.

Conclusion

We reveal significant differences in the gut microbiota between obese and lean adult Emiratis and an association between certain microbial genera of the gut microbiota and obesity. A better understanding of the interactions between gut microbes, diet, lifestyle, and health is warranted.

Ultraprocessed Foods and Obesity Risk: A Critical Review of Reported Mechanisms

Epidemiologic evidence supports a positive association between ultraprocessed food (UPF) consumption and body mass index. This has led to recommendations to avoid UPFs despite very limited evidence establishing causality. Many mechanisms have been proposed, and this review critically aimed to evaluate selected possibilities for specificity, clarity, and consistency related to food choice (i.e., low cost, shelf-life, food packaging, hyperpalatability, and stimulation of hunger/suppression of fullness); food composition (i.e., macronutrients, food texture, added sugar, fat and salt, energy density, low-calorie sweeteners, and additives); and digestive processes (i.e., oral processing/eating rate, gastric emptying time, gastrointestinal transit time, and microbiome). For some purported mechanisms (e.g., fiber content, texture, gastric emptying, and intestinal transit time), data directly contrasting the effects of UPF and non-UPF intake on the indices of appetite, food intake, and adiposity are available and do not support a unique contribution of UPFs. In other instances, data are not available (e.g., microbiome and food additives) or are insufficient (e.g., packaging, food cost, shelf-life, macronutrient intake, and appetite stimulation) to judge the benefits versus the risks of UPF avoidance. There are yet other evoked mechanisms in which the preponderance of evidence indicates ingredients in UPFs actually moderate body weight (e.g., low-calorie sweetener use for weight management; beverage consumption as it dilutes energy density; and higher fat content because it reduces glycemic responses). Because avoidance of UPFs holds potential adverse effects (e.g., reduced diet quality, increased risk of food poisoning, and food wastage), it is imprudent to make recommendations regarding their role in diets before causality and plausible mechanisms have been verified.

Butyrate in Human Milk: Associations with Milk Microbiota, Milk Intake Volume, and Infant Growth

Butyrate in human milk (HM) has been suggested to reduce excessive weight and adipo-sity gains during infancy. However, HM butyrate's origins, determinants, and its influencing mechanism on weight gain are not completely understood. These were studied in the prospective longitudinal Cambridge Baby Growth and Breastfeeding Study (CBGS-BF), in which infants (n = 59) were exclusively breastfed for at least 6 weeks. Infant growth (birth, 2 weeks, 6 weeks, 3 months, 6 months, and 12 months) and HM butyrate concentrations (2 weeks, 6 weeks, 3 months, and 6 months) were measured. At age 6 weeks, HM intake volume was measured by deuterium-labelled water technique and HM microbiota by 16S sequencing. Cross-sectionally at 6 weeks, HM butyrate was associated with HM microbiota composition (p = 0.036) although no association with the abundance of typical butyrate producers was detected. In longitudinal analyses across all time points, HM butyrate concentrations were overall negatively associated with infant weight and adiposity, and associations were stronger at younger infant ages. HM butyrate concentration was also inversely correlated with HM intake volume, supporting a possible mechanism whereby butyrate might reduce infant growth via appetite regulation and modulation of HM intake.

Type, Intensity, and Duration of Exercise as Regulator of Gut Microbiome Profile

ABSTRACT

Gut microbiome profile is related to individual health. In metabolic syndrome, there is a change in the gut microbiome profile, indicated by an increase in the ratio of Firmicutes to Bacteroidetes. Many studies have been conducted to determine the effect of exercise on modifying the gut microbiome profile. The effectiveness of exercise is influenced by its type, intensity, and duration. Aerobic training decreases splanchnic blood flow and shortens intestinal transit time. High-intensity exercise improves mitochondrial function and increases the essential bacteria in lactate metabolism and urease production. Meanwhile, exercise duration affects the hypothalamic-pituitary-adrenal axis. All of these mechanisms are related to each other in producing the effect of exercise on the gut microbiome profile.

The composition of the gut microbiome differs among community dwelling older people with good and poor appetite

BACKGROUND

Anorexia of ageing is common and important in the development of sarcopenia in older individuals. Links have been proposed between the gut microbiota and sarcopenia. Disordered gut function is also recognized in anorexia of ageing, but how this may relate to resident gut microbiota is unexplored. Understanding this relationship may provide a basis for novel interventions for anorexia of ageing and sarcopenia. This study explores compositional differences of the gut microbiota between community dwelling healthy older adults with good or poor appetite, and associated differences in sarcopenia.

METHODS

We assessed appetite by the Simplified Nutritional Appetite Questionnaire (SNAQ) in members of the TwinsUK cohort aged ≥65 years. Using a pool of 776 individuals with existing microbiome data estimated from 16S rRNA sequencing data, we identified 102 cases (SNAQ score < 14) (95% female, mean age 68 years) matched to controls (SNAQ > 14) on body mass index, gender, age, diet, calorie consumption, frailty, antibiotic use, socio-economic status, and technical variables to minimize confounding microbiota associations. Species abundance and diversity, compositional differences, and paired differences in taxa abundance were compared between cases and controls. Additionally, we compared case and controls for sarcopenia as measured by muscle mass (appendicular lean mass/height² ) and strength (chair stand time in seconds).

RESULTS

Cases with poor appetite had reduced species richness and diversity of their gut microbiome (adjusted OBSERVED: beta = -0.2, P < 0.001; adjusted SHANNON: beta = -0.17, P = 0.0135), significant compositional differences (adjusted non-parametric multivariate analysis of variance, P = 0.0095), and significant differences in taxa abundance including reduction of genus Lachnospira (logFC = -1.015, q = 0.023). In all-female subgroup analysis, cases with poor appetite demonstrated reduction in muscle strength (11.03 s vs. 9.26 s, P = 0.02).

CONCLUSIONS

This study is the first to observe differences in the composition of gut microbiota between healthy community dwelling older individuals with good and poor appetite. We found female individuals with reduced muscle strength had poor appetite compared with those with normal strength. These associations require further examination to understand causality and mechanisms of interaction, to inform potential strategies targeting the gut microbiota as a novel intervention for anorexia of ageing and sarcopenia.

Regulating appetite in broilers for improving body and muscle development - A review

Appetite is the desire for feed and water and the voluntary intake of feed and is an important regulator of livestock productivity and animal health. Economic traits such as growth rate and muscle development (meat deposition) in broilers are directly correlated to appetite. Factors that may influence appetite include environmental factors, such as stress and temperature variation, and animal‐specific factors, such as learning period, eating capacity and preferences. Feed preferences have been reported to be determined in early life, and this period is important in broilers due to their fast growth and relatively short growth trajectories. This may be of importance when contemplating the use of more circular and sustainable feeds and the optimization of appetite for these feeds. The objective of this review was to review the biological mechanisms underlying appetite using data from human, animal and bird models and to consider the option for modulating appetite particularly as it relates to broiler chickens.

Trait-based community assembly and succession of the infant gut microbiome

The human gut microbiome develops over early childhood and aids in food digestion and immunomodulation, but the mechanisms driving its development remain elusive. Here we use data curated from literature and online repositories to examine trait-based patterns of gut microbiome succession in 56 infants over their first three years of life. We also develop a new phylogeny-based approach of inferring trait values that can extend readily to other microbial systems and questions. Trait-based patterns suggest that infant gut succession begins with a functionally variable cohort of taxa, adept at proliferating rapidly within hosts, which gradually matures into a more functionally uniform cohort of taxa adapted to thrive in the anoxic gut and disperse between anoxic patches as oxygen-tolerant spores. Trait-based composition stabilizes after the first year, while taxonomic turnover continues unabated, suggesting functional redundancy in the traits examined. Trait-based approaches powerfully complement taxonomy-based approaches to understanding the mechanisms of microbial community assembly and succession.

Recent efforts have been made to apply ecological theory on succession to understand the dynamics of human microbiomes throughout development. Here, Guittar et al. use a trait-based approach to show how microbial traits putatively related to dispersal and environmental tolerance shift in the infant microbiome over the first three years of life.

Catechin supplemented in a FOS diet induces weight loss by altering cecal microbiota and gene expression of colonic epithelial cells

The present study showed that catechin controlled rats’ body weights by altering gut microbiota and gene expression of colonic epithelial cells when supplemented into a high-fructo-oligosaccharide (FOS) diet.

Weight-loss interventions and gut microbiota changes in overweight and obese patients: a systematic review

Imbalances in the gut microbiota, the bacteria that inhabit the intestines, are central to the pathogenesis of obesity. This systematic review assesses the association between the gut microbiota and weight loss in overweight/obese adults and its potential manipulation as a target for treating obesity. This review identified 43 studies using the keywords 'overweight' or 'obesity' and 'microbiota' and related terms; among these studies, 17 used dietary interventions, 11 used bariatric surgery and 15 used microbiota manipulation. The studies differed in their methodologies as well as their intervention lengths. Restrictive diets decreased the microbiota abundance, correlated with nutrient deficiency rather than weight loss and generally reduced the butyrate producers Firmicutes, Lactobacillus sp. and Bifidobacterium sp. The impact of surgical intervention depended on the given technique and showed a similar effect on butyrate producers, in addition to increasing the presence of the Proteobacteria phylum, which is related to changes in the intestinal absorptive surface, pH and digestion time. Probiotics differed in strain and duration with diverse effects on the microbiota, and they tended to reduce body fat. Prebiotics had a bifidogenic effect and increased butyrate producers, likely due to cross-feeding interactions, contributing to the gut barrier and improving metabolic outcomes. All of the interventions under consideration had impacts on the gut microbiota, although they did not always correlate with weight loss. These results show that restrictive diets and bariatric surgery reduce microbial abundance and promote changes in microbial composition that could have long-term detrimental effects on the colon. In contrast, prebiotics might restore a healthy microbiome and reduce body fat.

Adult Intake of Minimally Processed Fruits and Vegetables: Associations with Cardiometabolic Disease Risk Factors

BACKGROUND

The US Department of Agriculture launched ChooseMyPlate.gov nutrition recommendations designed to encourage increased fruit and vegetable intake, in part, as a strategy for improving weight control through the consumption of high-satiation foods.

OBJECTIVE

The purpose of this cross-sectional study was to assess the relationship between adults' reported daily intake of fruits and nonstarchy vegetables (ie, those thought to have the lowest energy density) expressed as a proportion of their total daily food intake and objectively measured cardiovascular and metabolic disease risk factors using data from the 2009-2010 National Health and Nutrition Examination Survey (NHANES). Physical activity was included as a moderator variable.

DESIGN

This study employed a cross-sectional examination of 2009-2010 NHANES data to assess how daily fruit and nonstarchy vegetable intake was associated with anthropometric measures and cardiometabolic blood chemistry markers.

PARTICIPANTS/SETTING

Adults free of cardiac or metabolic disease (n=1,197) participated in 24-hour dietary recalls; a variety of cardiometabolic biomarkers and anthropometric measures were also collected from participants.

MAIN OUTCOME MEASURES

Among participants with complete data on all variables, the ratio of the combined cup-equivalents of fruit and nonstarchy vegetable intake to the total gram weight of all foods consumed daily (F/V ratio) served as the primary independent variable. Main dependent measures included fasting glucose, insulin, glycosylated hemoglobin, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, total cholesterol, waist circumference, and body mass index.

STATISTICAL ANALYSES PERFORMED

Demographic and behavioral predictors of the F/V ratio and the association between the F/V ratio and cardiometabolic disease risk factors were examined using multivariate regression.

RESULTS

Body mass index (β=-2.58; 95% CI -3.88 to -1.28), waist circumference (β=-6.33; 95% CI -9.81 to -2.84), and insulin (β=-0.21; 95% CI -0.37 to -0.05) were inversely associated with the F/V ratio. These associations were weakened for the subset that adhered to federal physical activity recommendations. No other statistically significant associations were found between F/V ratio and main dependent measures.

CONCLUSIONS

In this nationally representative sample, predicted inverse associations between the proportion of daily fruit and nonstarchy vegetable intake relative to total intake and measures reflective of body fat composition and fasting insulin were confirmed. Future research should examine whether a similar association is observed for other sources of resistant starch, such as whole grains, which are arguably more strongly linked with satiety and host insulin levels.

Obesity Reduces Cognitive and Motor Functions across the Lifespan

Due to a sedentary lifestyle, more and more people are becoming obese nowadays. In addition to health-related problems, obesity can also impair cognition and motor performance. Previous results have shown that obesity mainly affects cognition and motor behaviors through altering brain functions and musculoskeletal system, respectively. Many factors, such as insulin/leptin dysregulation and inflammation, mediate the effect of obesity and cognition and motor behaviors. Substantial evidence has suggested exercise to be an effective way to improve obesity and related cognitive and motor dysfunctions. This paper aims to discuss the association of obesity with cognition and motor behaviors and its underlying mechanisms. Following this, mechanisms of exercise to improve obesity-related dysfunctions are described. Finally, implications and future research direction are raised.

Dietary and Policy Priorities for Cardiovascular Disease, Diabetes, and Obesity: A Comprehensive Review

Suboptimal nutrition is a leading cause of poor health. Nutrition and policy science have advanced rapidly, creating confusion yet also providing powerful opportunities to reduce the adverse health and economic impacts of poor diets. This review considers the history, new evidence, controversies, and corresponding lessons for modern dietary and policy priorities for cardiovascular diseases, obesity, and diabetes mellitus. Major identified themes include the importance of evaluating the full diversity of diet-related risk pathways, not only blood lipids or obesity; focusing on foods and overall diet patterns, rather than single isolated nutrients; recognizing the complex influences of different foods on long-term weight regulation, rather than simply counting calories; and characterizing and implementing evidence-based strategies, including policy approaches, for lifestyle change. Evidence-informed dietary priorities include increased fruits, nonstarchy vegetables, nuts, legumes, fish, vegetable oils, yogurt, and minimally processed whole grains; and fewer red meats, processed (eg, sodium-preserved) meats, and foods rich in refined grains, starch, added sugars, salt, and trans fat. More investigation is needed on the cardiometabolic effects of phenolics, dairy fat, probiotics, fermentation, coffee, tea, cocoa, eggs, specific vegetable and tropical oils, vitamin D, individual fatty acids, and diet-microbiome interactions. Little evidence to date supports the cardiometabolic relevance of other popular priorities: eg, local, organic, grass-fed, farmed/wild, or non-genetically modified. Evidence-based personalized nutrition appears to depend more on nongenetic characteristics (eg, physical activity, abdominal adiposity, gender, socioeconomic status, culture) than genetic factors. Food choices must be strongly supported by clinical behavior change efforts, health systems reforms, novel technologies, and robust policy strategies targeting economic incentives, schools and workplaces, neighborhood environments, and the food system. Scientific advances provide crucial new insights on optimal targets and best practices to reduce the burdens of diet-related cardiometabolic diseases.