Diet and obesity

Gut Microbes, Diet, and Genetics as Drivers of Metabolic Liver Disease: A Narrative Review Outlining Implications for Precision Medicine

Metabolic dysfunction-associated steatotic liver disease (MASLD) is rapidly increasing in prevalence, impacting over a third of the global population. The advanced form of MASLD, Metabolic dysfunction-associated steatohepatitis (MASH), is on track to become the number one indication for liver transplant. FDA-approved pharmacological agents are limited for MASH, despite over 400 ongoing clinical trials, with only a single drug (resmetirom) currently on the market. This is likely due to the heterogeneous nature of disease pathophysiology, which involves interactions between highly individualized genetic and environmental factors. To apply precision medicine approaches that overcome interpersonal variability, in-depth insights into interactions between genetics, nutrition, and the gut microbiome are needed, given that each have emerged as dynamic contributors to MASLD and MASH pathogenesis. Here, we discuss the associations and molecular underpinnings of several of these factors individually and outline their interactions in the context of both patient-based studies and preclinical animal model systems. Finally, we highlight gaps in knowledge that will require further investigation to aid in successfully implementing precision medicine to prevent and alleviate MASLD and MASH.

The relationship between low-carbohydrate diet score, dietary insulin index and load with obesity in healthy adults

PURPOSE

Carbohydrate intake and insulinemic potential of diet are suggested to be correlated with the development of different chronic diseases. Considering the limited research on obesity, this study aimed to investigate the association of dietary insulin index (DII), dietary insulin load (DIL), and low-carbohydrate diet score (LCDS) with body weight and obesity in healthy adults.

METHODS

In this cross-sectional study, DII, DIL, and LCDS were calculated using relevant formulas based on dietary intakes obtained by a valid 168-item food frequency questionnaire, in 393 otherwise healthy adults of either normal-weight, overweight, or obese.

RESULTS

Individuals in the highest tertile of DIL and DII had respectively 73% (OR: 0.27, 95% CI 0.08-0.94, p = 0.049) and 50% (OR: 0.5, 95% CI 0.26-0.96, p = 0.038) lower odds of being overweight compared to the lowest tertile, after adjusting the effects of age, sex, and dietary energy intake. Participants in the highest tertile of DIL had 92% greater odds of being obese compared to the lowest tertile, but this association did not remain significant after adjusting the effect of energy intake. Individuals in the highest tertile of LCDS had about 2 times odds of being overweight compared with those in the lowest tertile (OR: 2.04, 95% CI 1.04-4.01, p = 0.049). There was no relationship between being obese and tertiles of LCDS.

CONCLUSION

Higher dietary carbohydrate intake and insulinemic potential of diet could not be considered independent dietary risk factors for overweight or obesity.

LEVEL OF EVIDENCE

Level III: evidence obtained from an observational study.

A feasibility study of a WhatsApp-delivered Transtheoretical Model-based intervention to promote healthy eating habits for firefighters in Hong Kong: a cluster randomized controlled trial

BACKGROUND

Firefighters' health is often affected by a high prevalence of obesity and cardiovascular diseases, which are common risk factors for sudden cardiac death. The aim of this study is to investigate the feasibility of enhancing healthy eating habits in firefighters through an education programme.

METHODS

This will be a cluster randomized control trial study. The participants will be assigned randomly into either control (health promotion pamphlet) or intervention (health promotion pamphlet and education materials through WhatsApp) groups. Changes in healthy eating habits will be assessed by a self-administered questionnaire and anthropometric measurements at three different time points.

DISCUSSION

More education is required in order to improve firefighters' eating habits.

TRIAL REGISTRATION

ISRCTN registry identifier: Registered on 8 April 2019 ISRCTN95472464.

Associations between dietary insulin load with cardiovascular risk factors and inflammatory parameters in elderly men: a cross-sectional study

Given the limited research on dietary insulin load (DIL), we examined DIL in relation to cardiovascular risk factors and inflammatory biomarkers in elderly men. For the present cross-sectional study, we recruited 357 elderly men. Dietary intake was assessed using FFQ. DIL was estimated by multiplying the insulin index of each food by its energy content and frequency of consumption and then summing the final value of all food items. After adjustment for covariates, a significant positive association was observed between high DIL with fasting blood sugar (FBS) levels (OR: 7·52; 95 % CI 3·38, 16·75; P=0·0001) and high-sensitive C-reactive protein (hs-CRP) (OR: 3·03; 95 % CI 1·54, 5·94; P=0·001). However, there was no association between high DIL and BMI (OR: 1·43; 95 % CI 0·75, 2·75; P=0·27), serum TAG level (OR: 0·82; 95 % CI 0·26, 2·59; P=0·73), HDL-cholesterol (OR: 2·03; 95 % CI 0·79, 5·23; P=0·13) and fibrinogen (OR: 1·57; 95 % CI 0·80, 3·06; P=0·18). Overall, elderly men with high DIL had higher FBS and hs-CRP levels than those with low DIL. Future studies are needed to clarify the association between DIL and other cardiovascular risk factors in both men and women.

The Synergism in Hormonal and Cellular Changes in Male Mice on Long Term High Fat Exposure

OBJECTIVE

To determine the hormonal changes that occur as a result of the long-term intake of a very-high-fat diet (VHFD) that leads to simultaneous changes in the islets of Langerhans and adipocyte cell size.

METHODS

Male mice were fed with a normal chow diet (ND, n = 15) and a VHFD (n = 30) for 2, 12, and 24 weeks. Body weight, food intake, caloric intake (fat [saturated and unsaturated], protein, and carbohydrate), hormone levels (leptin and insulin), and islet of Langerhans/adipocyte size were quantitatively recorded.

RESULTS

In VHFD-fed animals, body weight showed a significant percent increase within the first 12 weeks and then plateaued with time. VHFD-fed animals consumed significantly less food than ND at all time periods, indicating that it was the quality of food and not the quantity that caused this increase in body weight. Male mice on VHFD showed a significant increase in leptin and insulin levels, along with accompanying growth in islet and adipocyte size within the first 12 weeks, which plateaued as the mice aged. The increases in the islet and adipocyte size in VHFD-fed animals were similar to the analogous increases in hormonal levels (2 vs. 12 vs. 24 weeks). These results, therefore, suggest that in diet-induced obesity changes, shifts in hormonal levels works hand-in-hand with metabolic adjustments at the cellular level to combat the effect of fat.

CONCLUSION

Thus, mechanisms like hormonal resistance, changes in adiposity, islet size, and caloric intake with prolonged exposure to high fat are probably defensive mechanisms employed to protect against diabetes. In order to understand these complicated and nuanced effects of high fat and to comprehend the underlying mechanism associated with it, it is important to focus on long-term studies that emphasize the synergy between cellular and hormonal changes, in addition to an analysis of individual components.

The Impact of Sleep Improvement on Food Choices in Adolescents With Late Bedtimes

PURPOSE

The aim was to investigate the effect of sleep improvement on desire for and intake of weight gain-promoting foods in adolescents with late bedtimes.

METHODS

A sample of 42 adolescents with late bedtimes was enrolled in an intervention designed to improve sleep. Their desire for and intake of food in the morning was assessed at before and after treatment.

RESULTS

Adolescents with earlier bedtimes at post-treatment relative to pretreatment increased their caloric intake of low glycemic index, fruit, and dairy foods at post-treatment. This effect was not observed in adolescents who did not improve their bedtime at post-treatment.

CONCLUSIONS

These findings suggest that advancing bedtimes earlier can improve breakfast choices, an important meal for obesity prevention during adolescence.

Long-Term High Fat Diet Has a Profound Effect on Body Weight, Hormone Levels, and Estrous Cycle in Mice

Background

Obesity causes several health complications along with disruption of the reproductive system. The aim of the current study was to determine how long-term intake of very high fat diet (VHFD) changes the hormonal milieu, affecting the cellular morphology and reproductive cycle in female mice.

Material/Methods

Mice were fed on normal diet (ND) and VHFD for 2 weeks, 12 weeks, and 25–27 weeks. We assessed changes in body weight, food consumption, energy intake, cellular and tissue morphology, hormonal levels (leptin, insulin, and estradiol), and vaginal smears were performed at various time points to determine the length and cellularity at each stage of the estrous cycle.

Results

Mice fed on VHFD showed a significant increase in weight gain, reduction in food intake, and increase in energy intake compared to animals fed on ND, indicating that the caloric density of the diet is responsible for the differences in weight gain. Hormonal analysis showed hyperleptinemia, hyperinsulinemia, and increases in estrogen levels, along with increases in size of the islet of Langerhans and adipocytes. After 25–27 weeks, all animals fed on VHFD showed complete acyclicity; elongation of phases (e.g., diestrous), skipping of phases (e.g., metestrous), or a combination of both, indicating disruption in the reproductive cycle. Quantitative analysis showed that in the diestrous phase there was a 70% increase in cell count in VHFD compared to animals fed on ND.

Conclusions

The above results show that morphological and hormonal changes caused by VHFD probably act via negative feedback to the hypothalamic-pituitary axis to shut down reproduction, which has a direct effect on the estrous cycle, causing acyclicity in mice.

Exposure to a diet high in fat attenuates dendritic spine density in the medial prefrontal cortex

A key factor in the development of obesity is the overconsumption of food calorically high in fat. Overconsumption of food high in fat not only promotes weight gain but elicits changes in reward processing. No studies to date have examined whether consumption of a high-fat (HF) diet alters structural plasticity in brain areas critical for reward processing, which may account for persistent changes in behavior and psychological function by reorganizing synaptic connectivity. To test whether dietary fat may induce structural plasticity we placed rats on one of three dietary conditions: ad libitum standard chow (SC), ad libitum 60 % HF (HF-AL), or calorically matched 60 % HF (HF-CM) for 3 weeks and then quantified dendritic spine density and type on basal and apical dendrites of pyramidal cells in layer V of the medial prefrontal cortex (mPFC) and medium spiny neurons (MSNs) of the nucleus accumbens. Our results demonstrate a significant reduction in the density of thin spines on the apical and basal segments of dendrites within the infralimbic, but not prelimbic, mPFC.

Efecto de la administración subcrónica de glucosamina oral en la regulación del peso corporal, glucemia y dislipidemias provocada por una dieta hipercalórica en rata Wistar

Objetivo: Este estudio evaluó el efecto de la glucosamina oral en el sobrepeso y dislipidemia provocada por una dieta hipercalórica en ratas.Métodos: En 4 grupos de ratas Wistar: alimentados con dieta comercial para roedores y agua de beber sin grupo de control y con glucosamina (500 mg/kg-1 por día) grupo glucosamina y con dieta hipercalórica enriquecida al 24% (g/g) compuesta por manteca de cerdo y agua de beber sin grupo hipercalórico y con glucosamina grupo hipercalórico + grupo glucosamina, durante 22 semanas, se evaluaron el peso corporal, grasa abdominal, niveles de glucemia, triglicéridos, colesterol total y lipoproteínas de alta densidad en suero.Resultados: Se observó un aumento del peso corporal y glucemia en suero con dislipidemias en el grupo con dieta hipercalórica grupo hipercalórico versusgrupo de controle (p<0.001); al administrarse glucosamina para esta misma dieta grupo hipercalórico + grupo glucosamina se minimizaron los efectos presentados, disminuyendo la cantidad de grasa abdominal y los niveles del perfil lípido en suero (p>0.05) y regulándose el peso corporal, las lipoproteínas de alta densidad y la glucemia basal (p<0.05).Conclusion: La glucosamina reguló el peso corporal y la glucemia en sangre y minimizó las dislipidemias provocadas por la dieta hipercalórica, favoreciendo el aumento de colesterol lipoproteínas de alta densidad en las ratas. No afectó el peso corporal y el metabolismo lipídico cuando se administró con dieta comercial.

Rurality and dietary patterns: associations in a UK cohort study of 10-year-old children

Objective

Despite differences in obesity and ill health between urban and rural areas in the UK being well documented, very little is known about differences in dietary patterns across these areas. The present study aimed to examine whether urban/rural status is associated with dietary patterns in a population-based UK cohort study of children.

Design

Dietary patterns were obtained using principal components analysis and cluster analysis of 3 d diet records collected from children at 10 years of age. Rurality was obtained from the 2001 UK Census urban/rural indicator at the time of dietary assessment. General linear models were used to examine the relationship between rurality and dietary pattern scores from principal components analysis; multinomial logistic regression was used to assess the association between rurality and dietary clusters.

Setting

The Avon Longitudinal Study of Parents and Children (ALSPAC), South West England.

Subjects

Children (n 5677) aged 10 years (2817 boys and 2860 girls).

Results

After adjustment, increases in rurality were associated with increased scores on the ‘health awareness’ dietary pattern (β=0·35; 95 % CI 0·14, 0·56; P<0·001 for the most rural compared with the most urban group) and lower scores on the ‘packed lunch/snack’ dietary pattern (β=−0·39; 95 % CI −0·59, −0·19; P<0·001 for the most rural compared with the most urban group). The odds ratio for participants being in the ‘healthy’ compared with the ‘processed’ dietary cluster for the most rural areas was 1·61 (95 % CI 1·05, 2·49; P=0·02) compared with those in the most urban areas.

Conclusions

There is evidence to suggest that differences exist in dietary patterns between rural and urban areas. Similar results were found using two different methods of dietary pattern analysis, showing that children residing in rural households were more likely to consume healthier diets than those in urban households.

Vegetarian diet, Seventh Day Adventists and risk of cardiovascular mortality: a systematic review and meta-analysis

BACKGROUND

Dietary interventions are an important component of cardiovascular risk factor management although their impact on cardiovascular risk and mortality remains uncertain. We have studied influence of a vegetarian diet on cardiovascular risk and mortality.

METHODS

We searched MEDLINE and EMBASE for comparative studies that evaluated clinical outcomes associated with vegetarian diet as compared to non-vegetarian controls or the general population. Relevant studies were pooled using random effects meta-analysis for risk of death, ischaemic heart disease (IHD) and cerebrovascular disease. We conducted subgroup analysis according to specific type of cohort (e.g. Seventh Day Adventist [SDA]) and gender.

RESULTS

Eight studies met the inclusion criteria with 183,321 participants (n=183,321). There was significant heterogeneity in all the meta-analyses, particularly evident with the studies of SDA. In all instances, we found that SDA studies showed greater effect size as compared to non-SDA studies: death (RR 0.68 95% CI 0.45-1.02 vs RR 1.04 95% CI 0.98-1.10), ischaemic heart disease (IHD) (RR 0.60 95% CI 0.43-0.80 vs RR 0.84 95% CI 0.74-0.96) and cerebrovascular disease (RR 0.71 95% CI 0.41-1.20 vs RR 1.05 95% CI 0.89-1.24). Sex specific analyses showed that IHD was significantly reduced in both genders but risk of death and cerebrovascular disease was only significantly reduced in men.

CONCLUSIONS

Data from observational studies indicates that there is modest cardiovascular benefit, but no clear reduction in overall mortality associated with a vegetarian diet. This evidence of benefit is driven mainly by studies in SDA, whereas the effect of vegetarian diet in other cohorts remains unproven.

Different dietary strategies for weight loss in obesity: role of energy and macronutrient content

Obesity is a chronic disorder caused by an imbalance of the energy metabolism with high associated burdens. Therefore, huge efforts are being currently devoted in studying new types of hypoenergetic diets and their composition, in order to characterise more specific, long-lasting and safe slimming protocols. A number of investigations are trying to determine the specific influence of the macronutrient distribution in energy-restricted diets on the management of excessive body weight. In this context, very-low-energy diets supplying between 1670 and 3350 kJ (400 and 800 kcal)/d have been beneficial in short-term treatments causing a weight loss of 300-500 g/d. Such strategies place more emphasis on energy restriction than on the macronutrient composition of the diet prescription. Weight loss produced by either low-carbohydrate or low-fat moderately energy-restricted diets ranges from 0.5 to 1.0 kg/week, while diets with high or moderately high protein content have also been applied in weight-reducing programmes by inducing losses of 0.2-0.4 kg/week. Other factors that determine weight loss by dieting are sex, age, initial body weight, race, genetics, regional fat deposition, etc, which must be taken into account to explain the variability in the outcomes of different low-energy diets. Therefore, more research is needed about the impact of diets with different fuel substrates and foods on the characteristics of the weight-loss process.

Microbiota and SCFA in lean and overweight healthy subjects

Obesity has recently been linked to the composition of human microbiota and the production of short chain fatty acids (SCFAs). However, these findings rely on experimental studies carried out using rather small and defined groups of volunteers or model animals. Our aim was to evaluate differences within the human intestinal microbiota and fecal SCFA concentration of lean and obese subjects. A total of 98 subjects volunteered to take part in this study. The BMI in kg/m(2) of 30 volunteers was within the lean range, 35 were overweight and 33 were obese. The fecal microbiota was characterized by real-time PCR analyses. With the primers used herein we were able to cover 82.3% (interquartile range of 68.3-91.4%) of the total microbiota detectable with a universal primer. In addition, the concentration of SCFA was evaluated. The total amount of SCFA was higher in the obese subject group (P = 0.024) than in the lean subject group. The proportion of individual SCFA changed in favor of propionate in overweight (P = 0.019) and obese subjects (P = 0.028). The most abundant bacterial groups in faeces of lean and obese subjects belonged to the phyla Firmicutes and Bacteroidetes. The ratio of Firmicutes to Bacteroidetes changed in favor of the Bacteroidetes in overweight (P = 0.001) and obese subjects (P = 0.005). Our results are in line with previous reports suggesting that SCFA metabolism might play a considerable role in obesity. However, our results contradict previous reports with regard to the contribution of various bacterial groups to the development of obesity and this issue remains controversial.

Antiobesity properties of two African plants (Afromomum meleguetta and Spilanthes acmella) by pancreatic lipase inhibition

Ethanol extracts of seeds of Afromomum meleguetta and flower buds of Splilanthes acmella presented pancreatic lipase inhibitory activities in a concentration related manner under in vitro conditions. The two plants were extracted with 70% ethanol by sonication, fractionated on silica gel and tested at concentrations in the range 0.75-2.0 mg/mL. Lipase inhibitory activities of 90% and 40% were observed in A. meleguetta and S. acmella, respectively. The two plants have potentials as candidates for weight reduction and obesity control.

Extreme obesity: a new medical crisis in the United States

The prevalence of obesity has markedly increased in the past few decades, and this disorder is responsible for more health care expenditures than any other medical condition. The greater the body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters), the greater the risk of comorbidities, including diabetes mellitus, hypertension, obstructive sleep apnea, many cancers, dyslipidemia, cardiovascular disease, and overall mortality. Class III (extreme) obesity, defined as a BMI of 40 kg/m2 or greater, has also increased such that it now affects almost 1 in 20 Americans. The prevalence of extreme obesity is greater among women than among men and greater among blacks than among non-Hispanic whites or Hispanics. The effect of extreme obesity on mortality is greater among young than among older adults, greater among men than among women, and greater among whites than among blacks. The current permissive environment that promotes increased dietary energy intake and decreased energy expenditure through reduced daily physical activity coupled with genetic susceptibility is an important pathogenic factor. The number of bariatric surgical procedures performed annually is relatively small but increasing.

Nutridynamics--studying the dynamics of food components in products and in the consumer

The concentrations and biological effects of nutrients, antinutrients and bioactive compounds, including microbes and their constituents, are affected by production and processing steps, the food matrix in which they reside, the way they are digested and metabolized in the human body, and whether or not and in what form they subsequently reach their target site. A new scientific concept, denoted here as 'nutridynamics', aims to unravel the dynamics of these processes by using a systematic approach to study how a food component is affected by the food matrix itself and what it does in the body. This holistic concept has potential synergy with the areas of food technology and nutrigenomics, and provides a link between food production and the mechanistic effects of bioactive ingredients.