Intentional weight loss in overweight and obese individuals and cognitive function: a systematic review and meta-analysis

Effects of exercise interventions on brain-derived neurotrophic factor levels in overweight and obesity: A systematic review and meta-analysis

Background

/Objective. An explosion in global obesity epidemic poses threats to the healthcare system by provoking risks of many debilitating diseases, including cognitive dysfunction. Physical activity has been shown to alleviate the deleterious effects of obesity-associated cognitive deficits across the lifespan. Given the strong neuroprotective role of brain-derived neurotrophic factor (BDNF) and exercise training as a known modulator for its elevation, this systematic review sought to examine the strength of the association between exercise and BDNF levels in healthy people with overweight and obesity.

Methods

Six electronic databases (PubMed, MEDLINE, EMBASE, Web of Science, Ovid Nursing Database, and SPORTDiscus) were searched from their inceptions through December 2022. The primary outcome of interest was BDNF levels. Interventional studies (randomized and quasi-experimental) with English full text available were included. Risk of bias of the included studies was assessed using the Physiotherapy Evidence Database Scale. Data were extracted for meta-analyses by random-effects models.

Results

Thirteen studies (n = 750), of which 69.2% (9/13) had low risk of bias, were included. In the meta-analysis, exercise interventions had no significant effect on resting BDNF levels (standardized mean difference: -0.30, 95% CI -0.80 to 0.21, P = 0.25). Subgroup analyses also indicated no effects of age and types of control groups being compared on moderating the association.

Conclusion

To further inform the role of BDNF in obesity-related cognitive functioning, rigorous studies with larger samples of participants and raw data available were imperatively deserved.

Astrocytes at the intersection of ageing, obesity, and neurodegeneration

Once considered passive cells of the central nervous system (CNS), glia are now known to actively maintain the CNS parenchyma; in recent years, the evidence for glial functions in CNS physiology and pathophysiology has only grown. Astrocytes, a heterogeneous group of glial cells, play key roles in regulating the metabolic and inflammatory landscape of the CNS and have emerged as potential therapeutic targets for a variety of disorders. This review will outline astrocyte functions in the CNS in healthy ageing, obesity, and neurodegeneration, with a focus on the inflammatory responses and mitochondrial function, and will address therapeutic outlooks.

Interactive Relations of Body Mass Index, Cardiorespiratory Fitness, and Sex to Cognitive Function in Older Adults

OBJECTIVE

The course of cognitive aging is influenced by multiple health factors. This cross-sectional study investigated the interactive relations between body mass index (BMI), maximum oxygen consumption (VO2max), and sex on neuropsychological outcomes in community-dwelling predominantly older adults.

METHODS

Participants were 164 healthy adults [M (SD) = 64.6 (12.5) years, 56% men, 87% white] who participated in an investigation of cardiovascular risk factors and brain health. Multivariable regression analysis, adjusted for age, education, ethnicity, smoking, alcohol consumption, and depression, examined the interactive relations of BMI, VO2max, and sex to multiple neuropsychological outcomes.

RESULTS

Significant BMI*VO2max*sex interactions for Grooved Pegboard dominant (p = .019) and nondominant (p = .005) hands revealed that men with lower VO2max (l/min) displayed worse performance with each hand as BMI increased (p's < .02). A significant BMI*sex interaction for Logical Memory-Delayed Recall (p = .036) (after adjustment for blood glucose) showed that men, but not women, with higher BMI demonstrated worse performance (p = .036). Lastly, significant main effects indicated that lower VO2max was related to poorer logical memory, and higher BMI was associated with poorer Trail Making B and Stroop interference scores (p's < .05).

CONCLUSIONS

Among men, higher cardiorespiratory fitness may protect against the negative impact of greater BMI on manual dexterity and motor speed, making VO2max a target for intervention. Higher BMI is further associated with poorer executive function and verbal memory (in men), and lower VO2max is associated with poorer verbal memory.

Inflammatory Pathways in Overweight and Obese Persons as a Potential Mechanism for Cognitive Impairment and Earlier Onset Alzeihmer's Dementia in the General Population: A Narrative Review

The overweight status or obesity can be confirmed through classical methods such as the body mass index (BMI) and the waist-to-hip ratio (WHR). Apart from metabolic issues such as atherosclerosis, liver steatosis, or diabetes mellitus, long-term obesity or overweight status can pose a risk for cardiovascular and neurovascular complications. While some acute adverse events like coronary syndromes of strokes are well-documented to be linked to an increased body mass, there are also chronic processes that, due to their silent onset and evolution, are underdiagnosed and not as thoroughly studied. Through this review, we aimed to collect all relevant data with regard to the long-term impact of obesity on cognitive function in all ages and its correlation with an earlier onset of dementia such as Alzheimer's disease (AD). The exact mechanisms through which a decline in cognitive functions occurs in overweight or obese persons are still being discussed. A combination of factors has been acknowledged as potential triggers, such as a sedentary lifestyle and stress, as well as a genetic predisposition, for example, the apolipoprotein E (ApoE) alleles in AD. Most research highlights the impact of vascular dysfunction and systemic inflammation on the nervous system in patients with obesity and the subsequent neurological changes. Obesity during the early to mid-ages leads to an earlier onset of cognitive dysfunction in various forms. Also, lifestyle intervention can reverse cognitive dysfunction, especially dieting, to encourage weight loss.

Effect of exercise interventions on brain-derived neurotrophic factor expression in people with overweight and obesity: protocol for a systematic review and meta-analysis

INTRODUCTION

Epidemic obesity ('globobesity') has led to a considerable rise in the prevalence and incidence of many disabling conditions, including cognitive dysfunction. Recent evidence has suggested that habitual exercise can alleviate the deleterious effects of obesity on cognitive functioning across the lifespan. Given that there is a potential link among obesity, exercise, cognitive health and brain-derived neurotrophic factor (BDNF), this systematic review aims to critically appraise interventional trials on exercise and BDNF and to estimate the pooled effect of exercise training on BDNF levels among healthy individuals with overweight and obesity.

METHODS AND ANALYSIS

Six electronic databases-PubMed, MEDLINE, EMBASE, Web of Science, Ovid Nursing Database and SPORTDiscus-will be searched from their inception through December 2022. Only interventional studies, including randomised controlled trials and quasi-experimental studies, with full text available and reported in English will be included. The primary outcomes will be changes in BDNF levels among healthy subjects with overweight and obesity following either acute or chronic bouts of exercise interventions. Two reviewers will independently conduct data extraction and risk of bias assessment for included trials using the Physiotherapy Evidence Database Scale. We will produce a narrative synthesis, with findings categorised by sex, age groups and types of exercise training. Data will be extracted and pooled for meta-analyses using random-effects models.

ETHICS AND DISSEMINATION

No formal ethical approval is required for this systematic review. The findings of this review will be disseminated through peer-reviewed publications.

PROSPERO REGISTRATION NUMBER

CRD42023414868.

Presurgical microstructural coherence predicts cognitive change for bariatric surgery patients

OBJECTIVE

This observational study examined the relationship between presurgical white matter microstructural coherence and cognitive change after weight loss. It was hypothesized that higher baseline fractional anisotropy (FA) would predict greater baseline and change cognition.

METHODS

A sample of 24 adults (BMI ≥ 35 kg/m2 ) underwent neuropsychological assessment at baseline and 12 weeks after bariatric surgery. A magnetic resonance imaging brain scan was administered at baseline and processed through Tract-Based Spatial Statistics to compute FA in white matter tracts of interest. Composite scores for attention, learning, processing speed, executive function, verbal fluency, working memory, and overall cognition were calculated.

RESULTS

As expected, FA in some tracts of interest was significantly (p < 0.05) positively associated with change in cognition. Inverse relationships were observed between baseline FA and presurgical cognition, which may be explained by increased medial and radial diffusivity and preserved axonal diffusivity. Cognition generally improved after surgery; however, relative but clinically nonsignificant deterioration was observed on learning measures. Poorer baseline cognitive performance was associated with greater postsurgical cognitive improvement.

CONCLUSIONS

Presurgical microstructural coherence is associated with magnitude of cognitive change after weight loss. An observed reduction in learning suggests that bariatric surgery may lead to negative outcomes in some cognitive domains, at least temporarily.

Exploring the Effects of a Mediterranean Diet and Weight Loss on the Gut Microbiome and Cognitive Performance in Older, African American Obese Adults: A Post Hoc Analysis

African American adults have a higher prevalence of Alzheimer's dementia (AD) than non-Hispanic Whites. The impact of a Mediterranean Diet (Med Diet) and intentional weight loss (IWL) on the gut microbiome may alter AD risk. A post hoc analysis of the Building Research in Diet and Cognition (BRIDGE) trial was performed to determine whether participation in an 8-month Med Diet lifestyle intervention with (n = 35) or without IWL (n = 31) was associated with changes in gut microbiota structure, abundance, and function and whether these changes were related to changes in cognitive performance. The results showed that family and genus alpha diversity increased significantly in both groups combined (p = 0.0075 and p = 0.024, respectively). However, there were no other significant microbially related within- or between-group changes over time. Also, an increase in Med Diet adherence was significantly associated with a decrease in alpha diversity at the phylum level only (p = 0.049). Increasing alpha diversity was associated with decreasing cognitive performance, but this association was attenuated after controlling for Med Diet adherence. In sum, an 8-month Med Diet lifestyle intervention with or without IWL did not appreciably alter the gut microbiome.

Association of daily-life functioning and obesity in individuals with schizophrenia and controls

Early weight gain following the diagnosis of schizophrenia (SCZ) has been associated with improved daily functioning. However, in the general population and in other psychiatric conditions such as bipolar disorder, increased body mass index (BMI) has been associated with worse functioning. The data on this association in chronic individuals with SCZ is still scarce. To address this gap in knowledge, our objective was to evaluate the association between BMI and psychosocial functioning in chronic outpatients with SCZ and in healthy individuals. Six-hundred individuals (n = 600), 312 with schizophrenia (SCZ) and 288 individuals with no personal or family history of severe mental illness (CTR), underwent weight, height and psychosocial functioning score (FAST) assessment. Linear regression models tested the association between FAST as dependent variable and BMI as independent variable, controlling for age, sex, use of clozapine and years of illness. In the CTR group, the highest BMI could predict a worse result in FAST, explaining about 22% of the variation found (Model: AdjR2 = 0.225 F(3,284) = 28.79 p < .001; BMI main effect: β = 0.509 t = 9.240 p < .001). In the SCZ group, there was no statistically significant association. Our findings corroborate the perception that increased BMI is associated with worse functioning status in the general population. In chronic SCZ, whatsoever, there is no association. Our findings suggest that patients with higher BMI in the SCZ group may compensate for the possible impairment of functionality due to increased body weight, through improved adherence and responsiveness to prescribed psychopharmacological treatment, leading to better control of psychiatric symptoms.

Association Between Late-Life Weight Change and Dementia: A Population-based Cohort Study

BACKGROUND

The impact of late-life weight changes on incident dementia is unclear. We aimed to investigate the associations of body mass index (BMI) and weight changes with dementia and to explore the role of APOE ɛ4 in these associations.

METHODS

A total of 1 673 dementia-free participants aged ≥60 and older were followed for an initial 6 years to detect changes in BMI/weight and then for an additional 6 years to detect incident dementia. BMI change ([BMIfirst 6-year follow-up - BMIbaseline]/BMIbaseline) was categorized as stable (≤5%), and moderate (5%-10%) or large (>10%) gain or loss. Weight change (weightfirst 6-year follow-up - weightbaseline) was categorized as stable (≤2.5 kg), and moderate (2.5-7.5 kg) or large (>7.5 kg) gain or loss. Dementia was diagnosed following standard criteria. Data were analyzed using Cox regression models.

RESULTS

Over the second 6-year follow-up period, 102 incident dementia cases were identified. Compared with stable BMI, the hazard ratios (95% CI) of dementia were 2.61 (1.09-5.54) and 2.93 (1.72-4.91) for BMI gain or loss >10%, respectively. The risk of dementia was higher among APOE ɛ4 carriers experiencing a large BMI gain (9.93 [3.49-24.6]) or loss (6.66 [2.83-14.4]) than APOE ɛ4 noncarriers with stable BMI. Similar results were observed for weight change and dementia associations.

CONCLUSIONS

BMI and weight changes showed U-shaped associations with dementia risk. Large bodyweight gain and loss alike are associated with an almost 3-fold higher risk of dementia, which may be amplified by APOE ɛ4.

Causality of abdominal obesity on cognition: a trans-ethnic Mendelian randomization study

BACKGROUND

Obesity has been associated with cognition in observational studies; however, whether its effect is confounding or a reverse causality remains inconclusive. This study aimed to investigate the causal relationships of overall obesity, measured by body mass index (BMI), and abdominal adiposity, measured by waist-hip ratio adjusted for BMI (WHRadjBMI), and cognition across European and Asian populations using Mendelian randomization (MR) analysis.

METHODS

We used publicly available genome-wide association study (GWAS) summary data of European ancestry, including BMI (n = 322,154) and WHRadjBMI (n = 210,088) from the GIANT consortium, and cognition performance (n = 257,828) from the UK Biobank and COGENT consortium. Data for individuals of Asian ancestry were retrieved from Taiwan Biobank to perform GWAS for BMI (n = 65,689), WHRadjBMI (n = 65,683), and Mini-Mental State Examination (MMSE, n = 21,273). MR analysis was carried out using the inverse-variance weighted method for the main results. Further, we examined the overall pleiotropy by MR-Egger intercept, and detected and adjusted for possible outliers using MR PRESSO.

RESULTS

No causal effect of BMI on cognition performance (beta [95% CI] = 0.00 [-0.07, 0.07], p value = 0.91) was found for Europeans; however, a 1-SD increase in WHRadjBMI was associated with a 0.07 standardized score decrease in cognition performance (beta [95% CI] = -0.07 [-0.12, -0.02], p value = 0.006). Further, no causal effect of BMI on MMSE (beta [95% CI] = 0.01 [-0.08, 0.10], p = 0.91) was found for Asians; however, a 1-SD increase in WHRadjBMI was associated with a 0.17 standardized score decrease in MMSE (beta [95% CI] = -0.17 [-0.30, -0.03], p = 0.02). In both populations, overall pleiotropy was not detected, and outliers did not affect the robustness of the main findings.

CONCLUSIONS

This trans-ethnic MR study reveals that abdominal adiposity, as measured by WHR adjusted for BMI, impairs cognition, whereas weak evidence suggests that BMI impairs cognition.

Overnutrition Induced Cognitive Impairment: Insulin Resistance, Gut-Brain Axis, and Neuroinflammation

Overnutrition-related obesity has become a worldwide epidemic, and its prevalence is expected to steadily rise in the future. It is widely recognized that obesity exerts negative impacts on metabolic disorders such as type 2 diabetes mellitus (T2DM) and cardiovascular diseases. However, relatively fewer reports exist on the impairment of brain structure and function, in the form of memory and executive dysfunction, as well as neurogenerative diseases. Emerging evidence indicates that besides obesity, overnutrition diets independently induce cognitive impairments via multiple mechanisms. In this study, we reviewed the clinical and preclinical literature about the detrimental effects of obesity or high-nutrition diets on cognitive performance and cerebral structure. We mainly focused on the role of brain insulin resistance (IR), microbiota-gut-brain axis, and neuroinflammation. We concluded that before the onset of obesity, short-term exposure to high-nutrition diets already blunted central responses to insulin, altered gut microbiome composition, and activated inflammatory mediators. Overnutrition is linked with the changes in protein expression in brain insulin signaling, leading to pathological features in the brain. Microbiome alteration, bacterial endotoxin release, and gut barrier hyperpermeability also occur to trigger mental and neuronal diseases. In addition, obesity or high-nutrition diets cause chronic and low-grade systematic inflammation, which eventually spreads from the peripheral tissue to the central nervous system (CNS). Altogether, a large number of unknown but potential routes interact and contribute to obesity or diet-induced cognitive impairment. The challenge for future research is to identify effective interventions involving dietary shifts and personalized therapy targeting the underlying mechanisms to prevent and improve cognition deficits.

The impact of different dark chocolate dietary patterns on synaptic potency and plasticity in the hippocampal CA1 area of the rats under chronic isolation stress

INTRODUCTION

Although, stress causes brain dysfunction, consumption of dark chocolate (DC) has positive effects on brain functions. The current study investigated the impact of different DC dietary patterns on synaptic potency and plasticity in the hippocampal CA1 area, as well as food intake and body weight in rats under chronic isolation stress.

METHODS

Thirty-five rats were allocated into five groups of control, stress, and stress accompanied by three DC dietary patterns (stress-compulsory, -optional, and -restricted DC). The stressed rats on a compulsory diet only received DC and the ones on an optional diet received unlimited chow and/or DC. Also, the stressed rats on a restricted diet each received chow freely and only 4 g DC daily. Subsequently, the slope and amplitude of field excitatory postsynaptic potentials (fEPSPs) were assessed based on the Input-Output (I/O) curves and after the longterm potentiation (LTP). Moreover, food intake and body weight were measured for all groups.

RESULTS

The fEPSP slope and amplitude in the I/O curves and after LTP decreased significantly in the stress group compared to the control group. Although the slope and amplitude both enhanced non-significantly in the optional DC diet, these parameters changed significantly in both compulsory and restricted DC dietary patterns compared to the stress group. Also, food intake and body weight decreased significantly in all DC groups.

CONCLUSION

The compulsory and restricted DC dietary patterns reversed the harmful effects of chronic isolation stress on the hippocampal synaptic potency, plasticity, learning, and memory. All DC diets, especially compulsory and restricted ones, reduced food intake and body weight.

Sex Differences in Cognition Across Aging

Sex and gender differences are seen in cognitive disturbances in a variety of neurological and psychiatry diseases. Men are more likely to have cognitive symptoms in schizophrenia whereas women are more likely to have more severe cognitive symptoms with major depressive disorder and Alzheimer's disease. Thus, it is important to understand sex and gender differences in underlying cognitive abilities with and without disease. Sex differences are noted in performance across various cognitive domains - with males typically outperforming females in spatial tasks and females typically outperforming males in verbal tasks. Furthermore, there are striking sex differences in brain networks that are activated during cognitive tasks and in learning strategies. Although rarely studied, there are also sex differences in the trajectory of cognitive aging. It is important to pay attention to these sex differences as they inform researchers of potential differences in resilience to age-related cognitive decline and underlying mechanisms for both healthy and pathological cognitive aging, depending on sex. We review literature on the progressive neurodegenerative disorder, Alzheimer's disease, as an example of pathological cognitive aging in which human females show greater lifetime risk, neuropathology, and cognitive impairment, compared to human males. Not surprisingly, the relationships between sex and cognition, cognitive aging, and Alzheimer's disease are nuanced and multifaceted. As such, this chapter will end with a discussion of lifestyle factors, like education and diet, as modifiable factors that can alter cognitive aging by sex. Understanding how cognition changes across age and contributing factors, like sex differences, will be essential to improving care for older adults.

Influence of Weight Loss on Cognitive Functions: A Pilot Study of a Multidisciplinary Intervention Program for Obesity Treatment

There is a relationship between obesity and cognitive functioning. Our aim was to assess weight loss influence on global cognition and executive functioning (EF) in adults with obesity under a multidisciplinary weight loss program. In this six-month longitudinal study, we assessed 81 adults (age < 50 years) with body mass index (BMI) ≥ 30. EF and global cognitive performance were evaluated with the Montreal Cognitive Assessment (MoCA), Neuropsychological Battery of Executive Functions (BANFE-2) and Trail Making Test-Part B (TMT-B). Median age was 40.0 years (IQR: 31.5−47, 61% women), and the median BMI was 41.4 (IQR: 36.7−45.9). At a six-month follow-up, the mean weight loss was 2.67% (29.6% of patients achieved ≥5% weight loss). There was an improvement in EF evaluated with BANFE (p = 0.0024) and global cognition with MoCA (p = 0.0024). Women experienced more remarkable change, especially in EF. Weight loss did not correlate with cognitive performance, except for TMT-B (r-0.258, p = 0.026). In the regression analysis, only years of education predicted the MoCA score. This study showed that patients improved cognitive performance during the follow-up; nevertheless, the magnitude of weight loss did not correlate with cognitive improvement. Future studies are warranted to demonstrate if patients achieving ≥5% weight loss can improve cognition, secondary to weight loss.

The relationship between physical activity, BMI, circadian rhythm, and sleep with cognition in bipolar disorder

BACKGROUND

Cognitive deficits affect a significant proportion of patients with bipolar disorder (BD). Problems with sustained attention have been found independent of mood state and the causes are unclear. We aimed to investigate whether physical parameters such as activity levels, sleep, and body mass index (BMI) may be contributing factors.

METHODS

Forty-six patients with BD and 42 controls completed a battery of neuropsychological tests and wore a triaxial accelerometer for 21 days which collected information on physical activity, sleep, and circadian rhythm. Ex-Gaussian analyses were used to characterise reaction time distributions. We used hierarchical regression analyses to examine whether physical activity, BMI, circadian rhythm, and sleep predicted variance in the performance of cognitive tasks.

RESULTS

Neither physical activity, BMI, nor circadian rhythm predicted significant variance on any of the cognitive tasks. However, the presence of a sleep abnormality significantly predicted a higher intra-individual variability of the reaction time distributions on the Attention Network Task.

CONCLUSIONS

This study suggests that there is an association between sleep abnormalities and cognition in BD, with little or no relationship with physical activity, BMI, and circadian rhythm.

Memory and eating: A bidirectional relationship implicated in obesity

This paper reviews evidence demonstrating a bidirectional relationship between memory and eating in humans and rodents. In humans, amnesia is associated with impaired processing of hunger and satiety cues, disrupted memory of recent meals, and overconsumption. In healthy participants, meal-related memory limits subsequent ingestive behavior and obesity is associated with impaired memory and disturbances in the hippocampus. Evidence from rodents suggests that dorsal hippocampal neural activity contributes to the ability of meal-related memory to control future intake, that endocrine and neuropeptide systems act in the ventral hippocampus to provide cues regarding energy status and regulate learned aspects of eating, and that consumption of hypercaloric diets and obesity disrupt these processes. Collectively, this evidence indicates that diet-induced obesity may be caused and/or maintained, at least in part, by a vicious cycle wherein excess intake disrupts hippocampal functioning, which further increases intake. This perspective may advance our understanding of how the brain controls eating, the neural mechanisms that contribute to eating-related disorders, and identify how to treat diet-induced obesity.

Peripheral versus central insulin and leptin resistance: Role in metabolic disorders, cognition, and neuropsychiatric diseases

Insulin and leptin are classically regarded as peptide hormones that play key roles in metabolism. In actuality, they serve several functions in both the periphery and central nervous system (CNS). Likewise, insulin and leptin resistance can occur both peripherally and centrally. Metabolic disorders such as diabetes and obesity share several key features including insulin and leptin resistance. While the peripheral effects of these disorders are well-known (i.e. cardiovascular disease, hypertension, stroke, dyslipidemia, etc.), the CNS complications of leptin and insulin resistance have come into sharper focus. Both preclinical and clinical findings have indicated that insulin and leptin resistance are associated with cognitive deficits and neuropsychiatric diseases such as depression. Importantly, these studies also suggest that these deficits in neuroplasticity can be reversed by restoration of insulin and leptin sensitivity. In view of these observations, this review will describe, in detail, the peripheral and central functions of insulin and leptin and explain the role of insulin and leptin resistance in various metabolic disorders, cognition, and neuropsychiatric diseases.

Interplay between cognition and weight reduction in individuals following a Mediterranean Diet: Three-year follow-up of the PREDIMED-Plus trial

BACKGROUND & AIMS

Some cognitive profiles might facilitate successful weight loss and its maintenance. Also, weight reductions may result in cognitive benefits. However, little work to date has examined the interactions between cognition and weight changes in the context of interventions with the Mediterranean diet (MedDiet). We studied the within-subject longitudinal relationships between cognition, body mass index (BMI), physical activity (PA), and quality of life (QoL), in older adults following a MedDiet.

METHODS

The PREDIMED-Plus is a primary prevention trial testing the effect of a lifestyle intervention program with an energy-restricted MedDiet (er-MedDiet), weight-loss goals and PA promotion on cardiovascular disease. The PREDIMED-Plus-Cognition sub-study included 487 participants (50% women, mean age 65.2 ± 4.7 years), with overweight/obesity, metabolic syndrome and normal cognitive performance at baseline. A comprehensive neurocognitive test battery was administered at baseline and after 1 and 3 years.

RESULTS

Baseline higher performance in verbal memory (OR = 1.5; 95%CI 1.0, 2.1), visuoconstructive praxis and attention (OR = 1.5; 95%CI 0.9, 2.3), and inhibition (OR = 1.3; 95%CI 0.9, 1.9) were associated with a higher odd of achieving at least 8% weight loss after 3 years follow-up in participants randomized to the intervention group. There were moderate improvements in specific tests of memory and executive functions during follow-up. Higher adherence to the er-MedDiet was associated with greater improvements in memory. Women exhibited lower rates of change in global cognition, PA and QoL. Moreover, improvements in memory correlated with reductions in BMI after 1 year (β_STD = -0.14) and with improvements in PA after 3 years (β_STD = 0.13). Finally, participants who experienced greater improvements in executive functions and global cognition also experienced greater improvements in their QoL.

CONCLUSIONS

This study refines the understanding of the determinants and mutual interrelationships between longitudinally-assessed cognitive performance and weight loss, adding further evidence to the cognitive benefits associated with better adherence to a MedDiet. Our results also suggest that weight loss interventions tailored to the cognitive profile and gender of participants are promising avenues for future studies.

Insulin resistance and NAFLD may influence memory performance in obese patients with prediabetes or newly-diagnosed type 2 diabetes

BACKGROUND AND AIMS

Diabetes has consistently been shown to increase risk for cognitive decline. Cognitive deficits may occur at the very earliest stages of diabetes. We sought to estimate the determinants of memory function in a group of middle-aged obese subjects with prediabetes or newly-diagnosed type 2 diabetes mellitus.

METHODS AND RESULTS

Sixty-two obese patients in treatment with metformin-with prediabetes (n = 41) or newly diagnosed T2DM (n = 21), were studied. Short- and long-term memory function was assessed through a neuropsychological assessment consisting of two tests and a composite domain z score was calculated. Cardiometabolic variables, such as abdominal MRI quantification of subcutaneous (SAT) and visceral (VAT) adipose tissue content, and of intra-hepatocellular lipid content, as well as insulin sensitivity (Matsuda Index, HOMA-IR) and beta cell performance (Beta Index), by multiple sampling, 8-point oral glucose tolerance test, were also evaluated. Age, non-alcoholic fatty liver disease (NAFLD), and lnHOMA-IR together explained 18% (R square) of the variance in memory domain. Including NAFLD increased the explained variance by 8% and including lnHOMA-IR by 9.1%, whereas the contribution of age and other factors was negligible.

CONCLUSION

Preventing and managing insulin resistance in precocious and possibly earlier stages of diabetes might provide benefit in slowering down future cognitive decline.

Legacy of a 10-Year Multidomain Lifestyle Intervention on the Cognitive Trajectories of Individuals with Overweight/Obesity and Type 2 Diabetes Mellitus

INTRODUCTION

Weight loss and increased physical activity interventions are commonly recommended for individuals with type 2 diabetes (T2D) and overweight or obesity. We examined the impact of randomization to an intensive lifestyle intervention (ILI) on trajectories of cognitive function over 10 years in a cohort of participants in a randomized clinical trial who had T2D and overweight/obesity at baseline.

METHODS

Participants aged 45-76 years were enrolled in 2001-2004 and were randomized to the ILI or a diabetes support and education (DSE) condition. Cognitive function was assessed in 3,938 participants at up to 4 time points 8-18 years after randomization. General linear mixed effects models examined cognitive trajectories over time. Subgroup analyses focused on sex, individuals with baseline body mass index >30, those carrying the APOE ε4 allele, and those with a baseline history of cardiovascular disease (CVD).

RESULTS

Overall, there were no differences in the rate of cognitive decline by intervention arm. Subgroup analyses showed that participants who had a baseline history of CVD and were randomized to the ILI arm of the study performed significantly worse on the Stroop Color Word Test than those in the DSE arm.

DISCUSSION/CONCLUSIONS

The ILI did not result in preserved cognitive function or slower rates of cognitive decline in this cohort of individuals who had T2D and were overweight or obese at baseline.

Cognitive response to testosterone replacement added to intensive lifestyle intervention in older men with obesity and hypogonadism: prespecified secondary analyses of a randomized clinical trial

BACKGROUND

Both obesity and hypogonadism are common in older men which could additively exacerbate age-related declines in cognitive function. However, little is known about the effects of lifestyle intervention plus testosterone replacement therapy in this population.

OBJECTIVES

In this secondary analysis of the LITROS (Lifestyle Intervention and Testosterone Replacement in Obese Seniors) trial, we examined whether testosterone replacement therapy would improve cognitive function when added to intensive lifestyle intervention in older men with obesity and hypogonadism.

METHODS

Eighty-three older, obese hypogonadal men with frailty were randomly assigned to lifestyle therapy (weight management and exercise training) plus testosterone (LT + Test) or lifestyle therapy plus placebo (LT + Pbo) for 6 mo. For this report, the primary outcome was change in the global cognition composite z score. Secondary outcomes included changes in z score subcomponents: attention/information processing, memory, executive function, and language. Changes between groups were analyzed using mixed-model repeated-measures ANCOVAs following the intention-to-treat principle.

RESULTS

Global cognition z score increased more in the LT + Test than in the LT + Pbo group (mean change: 0.49 compared with 0.21; between-group difference: -0.28; 95% CI: -0.45, -0.11; Cohen's d = 0.74). Moreover, attention/information z score and memory z score increased more in the LT + Test than in the LT + Pbo group (mean change: 0.55 compared with 0.23; between-group difference: -0.32; 95% CI: -0.55, -0.09; Cohen's d = 0.49 and mean change: 0.90 compared with 0.37; between-group difference: -0.53; 95% CI: -0.93, -0.13; Cohen's d = 1.43, respectively). Multiple regression analyses showed that changes in peak oxygen consumption, strength, total testosterone, and luteinizing hormone were independent predictors of the improvement in global cognition (R2 = 0.38; P < 0.001).

CONCLUSIONS

These findings suggest that in the high-risk population of older men with obesity and hypogonadism, testosterone replacement may improve cognitive function with lifestyle behaviors controlled via lifestyle intervention therapy.This trial was registered at clinicaltrials.gov as NCT02367105.

Association of Circulating Brain-Derived Neurotrophic Factor with Cognition among Adult Obese Population

Background

Obesity has a strong association with the risk of developing cognitive impairment and dementia at a later age. Brain-derived neurotrophic factor (BDNF) and its receptor appear to be important components in cognitive function and are also involved in energy homeostasis. The level of circulating BDNF and its association with cognition has yet to be delineated clearly. In this work we studied the association of circulating BDNF with cognition among the adult obese population.

Methods

The study involved 132 healthy participants between 18 and 40 years of age and of both sexes. The participants were categorized into an obesity group (n=66) and a non-obese group (n=66) based on their body mass index (Asian criteria). The level of cognitive performance was assessed by the event-related potentials P300 (ERPs-P300), mini-mental state examination (MMSE), both visual and auditory reaction times (VRT and ART, respectively), and other pen and paper tests related to memory and executive function. Serum BDNF, glycemic and lipid profiles were estimated.

Results

We found significant differences in the ERPs-P300 latency (P<0.001) and amplitude (P=0.002) between the non-obese and obese group. The MMSE score was significantly reduced while VRT (P=0.005) and ART (P=0.001) were larger in the obese group. BDNF levels (P<0.001) were significantly reduced and negatively associated with the obese group. ERPs-P300 latency was negatively associated (r=–0.674, P=0.001) whereas amplitude (r=0.507, P<0.001) was positively associated with the BDNF levels in the adult obese population.

Conclusion

We found reduced circulating BDNF levels in obese adults and that lower BDNF levels were strongly associated with cognitive decline in the obese adult population.

Weight Loss and the Risk of Dementia: A Meta-analysis of Cohort Studies

BACKGROUND

Weight loss is a common phenomenon among the elderly and is identified as an important indicator of health status. Many epidemiology studies have investigated the association between weight loss and dementia, but the results were inconsistent.

OBJECTIVE

To examine and determine the association between weight loss and the risk of dementia.

METHODS

Eligible cohort studies involving weight loss and dementia were searched from PubMed, Embase, and Ovid databases through October 2018. Pooled relative risks (RRs) with its 95% confidence intervals (CIs) were used to estimate the effects of weight loss on the risk of dementia. Subgroup and sensitivity analyses were performed to explore the potential sources of heterogeneity. The Begg's test and Egger's test were used to assess the publication bias.

RESULTS

A total of 20 cohort studies with 38,141 participants were included in this meta-analysis. Weight loss was significantly associated with the risk of dementia (RR=1.26, 95% CI=1.15-1.38). BMI decline ≥0.8 units (RR=1.31, 95% CI=1.10-1.56) and ≥4% (RR=1.19, 95% CI=1.03-1.38) could increase the risk of dementia. The risk of all-cause dementia for people with weight loss increased by 31% (RR=1.31, 95% CI=1.15-1.49), and 25% higher for incident Alzheimer's disease (RR=1.25, 95% CI=1.07-1.46). Weight loss in participants with normal weight had a similar dementia risk (RR=1.21, 95% CI=1.06-1.38) with the overweight individuals (RR=1.22, 95% CI=1.11-1.34).

CONCLUSION

Weight loss may be associated with an increased risk of dementia, especially for Alzheimer's disease. Maintaining weight stability may help prevent dementia.

Targeting the microbiome-gut-brain axis for improving cognition in schizophrenia and major mood disorders: A narrative review

Cognitive impairment has been consistently found to be a core feature of serious mental illnesses such as schizophrenia and major mood disorders (major depression and bipolar disorder). In recent years, a great effort has been made in elucidating the biological causes of cognitive deficits and the search for new biomarkers of cognition. Microbiome and gut-brain axis (MGB) hormones have been postulated to be potential biomarkers of cognition in serious mental illnesses. The main aim of this review was to synthesize current evidence on the association of microbiome and gut-brain hormones on cognitive processes in schizophrenia and major mood disorders and the association of MGB hormones with stress and the immune system. Our review underscores the role of the MGB axis on cognitive aspects of serious mental illnesses with the potential use of agents targeting the gut microbiota as cognitive enhancers. However, the current evidence for clinical trials focused on the MGB axis as cognitive enhancers in these clinical populations is scarce. Future clinical trials using probiotics, prebiotics, antibiotics, or faecal microbiota transplantation need to consider potential mechanistic pathways such as the HPA axis, the immune system, or gut-brain axis hormones involved in appetite control and energy homeostasis.

Clusterin and Its Role in Insulin Resistance and the Cardiometabolic Syndrome

The cardiometabolic syndrome involves a clustering of metabolic and cardiovascular factors which increase the risk of patients developing both Type 2 Diabetes Mellitus and cardio/cerebrovascular disease. Although the mechanistic underpinnings of this link remain uncertain, key factors include insulin resistance, excess visceral adiposity, atherogenic dyslipidemia, and endothelial dysfunction. Of these, a state of resistance to insulin action in overweight/obese patients appears to be central to the pathophysiologic process. Given the increasing prevalence of obesity-related Type 2 Diabetes, coupled with the fact that cardiovascular disease is the number one cause of mortality in this patient population, a more thorough understanding of the cardiometabolic syndrome and potential options to mitigate its risk is imperative. Inherent in the pathogenesis of insulin resistance is an underlying state of chronic inflammation, at least partly in response to excess adiposity. Within obese adipose tissue, an immunomodulatory shift occurs, involving a preponderance of pro-inflammatory immune cells and cytokines/adipokines, along with antigen presentation by adipocytes. Therefore, various adipokines differentially expressed by obese adipocytes may have a significant effect on cardiometabolism. Clusterin is a molecular chaperone that is widely produced by many tissues throughout the body, but is also preferentially overexpressed by obese compared lean adipocytes and relates strongly to multiple components of the cardiometabolic syndrome. Herein, we summarize the known and potential roles of circulating and adipocyte-specific clusterin in cardiometabolism and discuss potential further investigations to determine if clusterin is a viable target to attenuate both metabolic and cardiovascular disease.

The Role of Hypothalamic Inflammation in Diet-Induced Obesity and Its Association with Cognitive and Mood Disorders

Obesity is often associated with cognitive and mood disorders. Recent evidence suggests that obesity may cause hypothalamic inflammation. Our aim was to investigate the hypothesis that there is a causal link between obesity-induced hypothalamic inflammation and cognitive and mood disorders. Inflammation may influence hypothalamic inter-connections with regions important for cognition and mood, while it may cause dysregulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis and influence monoaminergic systems. Exercise, healthy diet, and glucagon-like peptide receptor agonists, which can reduce hypothalamic inflammation in obese models, could improve the deleterious effects on cognition and mood.

PART 3 Bypassing TBI: Metabolic Surgery and the Link Between Obesity and Traumatic Brain Injury-a Review

Obesity is a common outcome of traumatic brain injury (TBI) that exacerbates principal TBI symptom domains identified as common areas of post-TBI long-term dysfunction. Obesity is also associated with increased risk of later-life dementia and Alzheimer's disease. Patients with obesity and chronic TBI may be more vulnerable to long-term mental abnormalities. This review explores the question of whether weight loss induced by bariatric surgery could delay or perhaps even reverse the progression of mental deterioration. Bariatric surgery, with its induction of weight loss, remission of type 2 diabetes, and other expressions of the metabolic syndrome, improves metabolic efficiency, leads to reversal of brain lesions seen on imaging studies, and improves function. These observations suggest that metabolic/bariatric surgery may be a most effective therapy for TBI.

A Conceptual Model of Long-Term Weight Loss Maintenance: The Importance of Cognitive, Empirical and Computational Approaches

Living with obesity is related to numerous negative health outcomes, including various cancers, type II diabetes, and cardiovascular disease. Although much is known about the factors associated with obesity, and a range of weight loss interventions have been established, changing health-related behaviours to positively affect obesity outcomes has proven difficult. In this paper, we first draw together major factors that have emerged within the literature on weight loss to describe a new conceptual framework of long-term weight loss maintenance. Key to this framework is the suggestion that increased positive social support influences a reduction in psychosocial stress, and that this has the effect of promoting better executive functioning which in turn facilitates the development of healthy habits and the breaking of unhealthy habits, leading to improved ongoing maintenance of weight loss. We then outline how the use of computational approaches are an essential next step, to more rigorously test conceptual frameworks, such as the one we propose, and the benefits that a mixture of conceptual, empirical and computational approaches offer to the field of health psychology.

Adiposity, Inflammation, and Working Memory: Evidence for a Vicious Cycle

Overweight and obesity constitute the fifth leading cause of preventable deaths worldwide. One pathway through which excess weight contributes to poor health outcomes is via inflammatory activity and changes in cognitive processes. Prior theory has proposed a vicious cycle whereby obesity potentiates inflammatory activity, which alters cognitive processes such as working memory, which in turn leads to a reduced ability to self-regulate and therefore manage weight. However, to date no longitudinal studies have examined this potential dynamic. In the current study, we addressed this gap by assessing the relations among fat mass, C-reactive protein (CRP), and working memory across time in a large sample of 8536 children followed through adolescence in the Avon Longitudinal Study of Parents and Children in the United Kingdom. Adiposity was quantified via dual emission x-ray absorptiometry (DEXA) at ages 9 and 15.5 years old, and inflammatory activity was indexed via circulating serum C-reactive protein (CRP) levels assessed with a high-sensitivity assay at those same ages. Working memory was assessed between these two time points, at age 10, permitting examination of the temporal relations between working memory, adiposity, and inflammatory activity. As hypothesized, we found that fat mass predicted later poor working memory, and this association was statistically mediated by CRP. Further, we found that poor working memory predicted greater subsequent fat mass and CRP, and the link between working memory and subsequent CRP was partially mediated by fat mass. These results thus could be taken to suggest the existence of a vicious cycle of mutually amplifying adiposity, inflammatory activity, and poor working memory over time.

•

Adiposity and inflammatory activity (CRP) was measured at ages 9 and 15.5 ​yrs.

•

Working memory was assessed at age 10 ​yrs.

•

Adiposity predicted working memory, and this association was mediated by CRP.

•

Working memory predicted later adiposity and CRP, this was mediated by adiposity.

Visual, Verbal and Everyday Memory 2 Years After Bariatric Surgery: Poorer Memory Performance at 1-Year Follow-Up

Severe obesity has been associated with reduced performance on tests of verbal memory in bariatric surgery candidates. There is also some evidence that bariatric surgery leads to improved verbal memory, yet these findings need further elucidation. Little is known regarding postoperative memory changes in the visual domain and how patients subjectively experience their everyday memory after surgery. The aim of the current study was to repeat and extend prior findings on postoperative memory by investigating visual, verbal, and self-reported everyday memory following surgery, and to examine whether weight loss and somatic comorbidity predict memory performance. The study was a prospective, observational study in which participants (n = 48) underwent cognitive testing at baseline, 1 and 2 years after bariatric surgery. Repeated measures analyses of variance revealed significantly poorer visual and verbal memory performance at the 1-year follow-up, with performance subsequently returning to baseline levels after 2 years. Verbal learning and self-reported everyday memory did not show significant postoperative changes. Memory performance at 1 year was not significantly predicted by weight loss, changes in C-reactive protein levels or postoperative somatic comorbidity (Type 2 diabetes, sleep apnea, and hypertension). The study demonstrated poorer visual and verbal memory performance at 1-year follow-up that returned to baseline levels after 2 years. These findings are in contrast to most previous studies and require further replication, however, the results indicate that postoperative memory improvements following bariatric surgery are not universal. Findings suggest that treatment providers should also be aware of patients potentially having poorer memory at 1 year following surgery.

Part 2: Bypassing TBI-Metabolic Surgery and the Link Between Obesity and Traumatic Brain Injury-A Review

Obesity is a common outcome of traumatic brain injury (TBI) that exacerbates principal TBI symptom domains identified as common areas of post-TBI long-term dysfunction. Obesity is also associated with increased risk of later-life dementia and Alzheimer's disease. Patients with obesity and chronic TBI may be more vulnerable to long-term mental abnormalities. This review explores the question of whether weight loss induced by bariatric surgery could delay or perhaps even reverse the progression of mental deterioration. Bariatric surgery, with its induction of weight loss, remission of type 2 diabetes, and other expressions of the metabolic syndrome, improves metabolic efficiency, leads to reversal of brain lesions seen on imaging studies, and improves function. These observations suggest that metabolic/bariatric surgery may be the most effective therapy for TBI.

Building research in diet and cognition (BRIDGE): Baseline characteristics of older obese African American adults in a randomized controlled trial to examine the effect of the Mediterranean diet with and without weight loss on cognitive functioning

•

The MedDiet is correlated with slower cognitive decline in longitudinal studies.

•

Self-reported MedDiet adherence positively associated with select cognitive domains.

•

Women outperformed men across verbal tasks, including learning and memory.

•

Younger participants outperformed older participants on cognitive assessments.

In the United States, >5.4 million people age 65 and older are affected by cognitive impairment and dementia, including Alzheimer’s disease. African Americans are more likely than non-Hispanic whites to suffer from these disorders. Obesity is linked to accelerated age-related cognitive decline, and weight loss through caloric restriction is a potential strategy to prevent this cognitive impairment. Adherence to a healthful dietary pattern, such as the Mediterranean Diet (MedDiet), has also shown positive effects on reducing risk for dementia. African Americans are disproportionately affected by obesity and have less healthful diets than non-Hispanic whites. We present baseline characteristics from a three-arm randomized controlled trial that randomized 185 obese (BMI ≥ 30 kg/m² and ≤ 50 kg/m²) healthy older adults (55–85 years of age) to: 1) Typical Diet Control (TDC); 2) MedDiet alone (MedDiet-A) intervention; or 3) MedDiet caloric restricted intervention to promote weight loss (MedDiet-WL). The majority of the sample was African American (91.4%) and female (85.9%). The two active interventions (MedDiet-A and MedDiet-WL) met once weekly for 8 months, and the TDC received weekly general health newsletters. Baseline data were collected between January 2017 and July 2019 in Chicago, IL. In our sample, closer adherence to a MedDiet pattern was associated with higher attention and information processing (AIP) and higher executive functioning (EF). Consistent with the literature, we saw that older participants performed more poorly on the cognitive assessments than younger participants, and women outperformed men across verbally mediated tasks, especially ones related to learning and memory.

Cognition, Brain Structure, and Brain Function in Individuals with Obesity and Related Disorders

PURPOSE OF REVIEW

Obesity is one of the most serious public health concerns. Excess adipose tissue, particularly with a centralized distribution, is associated with cognitive decline. Indeed, obesity has been associated with a number of adverse changes in brain function and structure that can be detected by neuroimaging techniques. These obesity-associated changes in the brain are associated with cognitive dysfunction.

RECENT FINDINGS

While the pathways by which excess adipose tissue affects brain function are not fully understood, available evidence points towards insulin resistance, inflammation, and vascular dysfunction, as possible mechanisms responsible for the observed relations between obesity and cognitive impairment. It appears that weight loss is related to better brain and cognitive outcomes and that cognitive impairment due to obesity may be reversible.

C-Reactive Protein as a Possible Predictor of Trail-Making Performance in Individuals with Psychiatric Disorders

Cognitive dysfunction is a prominent feature of psychiatric disorders. Studies have shown that systemic low-grade inflammation is crucial in the development of cognitive deficits across psychiatric disorders. The aim of this study was to further examine the role of inflammation and inflammatory mediators in cognitive function in psychiatric disorders. This study included 364 inpatients (53% females) with International Classification of Diseases (ICD)-10 F3 (affective disorders) and F4 (neurotic, stress-related, and somatoform disorders) diagnoses. The mean age was 52 years (22 to 69 years) and the median body mass index was 27.6. Cognitive function was assessed with the Color–Word Interference Test after Stroop and the Trail-Making Test A/B. Multiple linear regression models were calculated to assess the predictive value of C-reactive protein and the kynurenine/tryptophan ratio on cognitive function controlling for age, sex, education, premorbid verbal intelligence quotient, illness duration, depressive symptoms, and obesity-related parameters (e.g., body mass index, high-density lipoprotein). Our data confirm that in patients with psychiatric disorders, C-reactive protein serum concentration is a relevant and important predictor of Trail-Making Test B performance, measuring cognitive flexibility. The effect size of this association did not change much after adding clinical and metabolic variables into the regression model. The kynurenine/tryptophan ratio was not related to cognitive test scores. The involvement of C-reactive protein as a peripheral inflammatory marker in cognitive flexibility and psychomotor processing speed in psychiatric illness can be concluded.

The Effects of a 12-Month Weight Loss Intervention on Cognitive Outcomes in Adults with Overweight and Obesity

Obesity is associated with poorer executive functioning and reward sensitivity. Yet, we know very little about whether weight loss through diet and/or increased exercise engagement improves cognitive function. This study evaluated whether weight loss following a dietary and exercise intervention was associated with improved cognitive performance. We enrolled 125 middle-aged adults with overweight and obesity (98 female) into a 12-month behavioral weight loss intervention. Participants were assigned to one of three groups: energy-restricted diet alone, an energy-restricted diet plus 150 min of moderate intensity exercise per week or an energy restricted diet plus 250 min of exercise per week. All participants completed tests measuring executive functioning and/or reward sensitivity, including the Iowa Gambling Task (IGT). Following the intervention, weight significantly decreased in all groups. A MANCOVA controlling for age, sex and race revealed a significant multivariate effect of group on cognitive changes. Post-hoc ANCOVAs revealed a Group × Time interaction only on IGT reward sensitivity, such that the high exercise group improved their performance relative to the other two intervention groups. Post-hoc ANCOVAs also revealed a main effect of Time, independent of intervention group, on IGT net payoff score. Changes in weight were not associated with other changes in cognitive performance. Engaging in a high amount of exercise improved reward sensitivity above and beyond weight loss alone. This suggests that there is additional benefit to adding exercise into behavioral weight loss regimens on executive functioning, even without additional benefit to weight loss.

Obesity and Brain Function: The Brain-Body Crosstalk

Dementia comprises a wide range of progressive and acquired neurocognitive disorders. Obesity, defined as excessive body fat tissue, is a common health issue world-wide and a risk factor for dementia. The adverse effects of obesity on the brain and the central nervous system have been the subject of considerable research. The aim of this review is to explore the available evidence in the field of body-brain crosstalk focusing on obesity and brain function, to identify the major research measurements and methodologies used in the field, to discuss the potential risk factors and biological mechanisms, and to identify the research gap as a precursor to systematic reviews and empirical studies in more focused topics related to the obesity-brain relationship. To conclude, obesity appears to be associated with reduced brain function. However, obesity is a complex health condition, while the human brain is the most complicated organ, so research in this area is difficult. Inconsistency in definitions and measurement techniques detract from the literature on brain-body relationships. Advanced techniques developed in recent years are capable of improving investigations of this relationship.

Effect of Long-Term Moderate Physical Exercise on Irisin between Normal Weight and Obese Men

BACKGROUND

Irisin is a myokine that has a beneficial effect on obesity and glucose metabolism by increasing energy expenditure. This study aims to investigate the effect of long-term moderate physical exercise on irisin levels and its correlations with body mass index (BMI), waist circumferences (WC), and metabolic parameters in normal weight and obese males. Material and method. A follow-up case-control study of sixty male participants, comprised of thirty normal weight and thirty obese, who had undergone supervised long-term moderate physical exercises for six months. Serum irisin levels, fasting blood glucose, serum insulin, homeostatic model assessment of the insulin resistance index (HOMA-IR), and β-cell function (HOMA-B2) were assessed.

RESULTS

Long-term moderate exercise induced elevation of the irisin level significantly (P < 0.0001) with significant reduction of the BMI, WC, fasting blood glucose, insulin, HOMA-IR, and HOMA-B2 levels (P < 0.0001) in comparison between obese and normal weight groups. There are significant differences for each parameter in each obese and normal weight group before and after physical exercise with exception of the BMI and WC in the normal group. Significant negative correlations were shown between irisin and blood glucose and insulin and HOMA-IR levels in the obese group and normal weight group.

CONCLUSION

Irisin improves glucose homeostasis after long-term moderate physical exercises, suggesting that irisin could have regulatory effect on glucose, insulin resistance, and obesity and it could be used as a potential therapy for obesity and insulin resistance.

Diet, inflammation and the gut microbiome: Mechanisms for obesity-associated cognitive impairment

Poor diet and obesity are associated with cognitive impairment throughout adulthood, and increased dementia risk in aging. Here we review the current literature interrogating the mechanisms by which diets high in fat, or fat and sugar lead to cognitive impairment, focusing on changes to gut microbiome composition, inflammatory signalling and blood-brain barrier integrity. Preclinical studies indicate weight gain is not necessary for diet-induced cognitive impairment. Rather, gut microbiome composition, and systemic and central inflammatory processes appear to contribute to diet-induced cognitive impairment. While both obese humans and rodents exhibit reduced blood-brain barrier integrity, cognitive impairments precede these changes, suggesting other mechanisms may underly diet-induced cognitive changes. Other potential candidates include hormone, glucoregulatory and cardiovascular changes. Poor diet and obesity act through multiple mechanisms to affect cognitive health and the challenge for future research is to identify key processes that can be reversed to improve cognition and quality of life.

Intensive weight loss and cognition: The dynamics of persistent organic pollutants in adipose tissue can explain the unexpected results from the Action for Health in Diabetes (Look AHEAD) study

OBJECTIVE

The aim of this paper is to propose a new hypothesis for the role of lipophilic chemical mixtures stored in adipose tissue in the development of dementia. Specifically, we present how the dynamics of these chemicals can explain the unexpected findings from the Action for Health in Diabetes (Look AHEAD) study, which failed to show long-term benefits of intentional weight loss on cognition, despite substantial improvements in many known risk factors for dementia. Moreover, we discuss how the role of obesity in the risk of dementia can change depending on the dynamics of these chemicals in adipose tissue.

NEW HYPOTHESIS

Human adipose tissue is widely contaminated with various neurotoxic chemicals. Typical examples are persistent organic pollutants (POPs), strong lipophilic chemicals with long half-lives. Both unintentional and intentional weight loss increases the release of POPs from adipocytes into the circulation. As POPs in the blood can easily reach the brain, the intentional weight-loss group of the Look AHEAD study may have experienced an unappreciated and long-term disadvantage on their cognition. Additionally, POPs may be involved in the link between obesity and dementia, as dysfunctional hypertrophic adipocytes enhance the release of POPs from adipocytes to the circulation through uncontrolled lipolysis. In contrast, metabolically healthy obese people may have a low risk of dementia because the safe storage of POPs in adipose tissue would decrease the amount of POPs reaching the brain.

MAJOR CHALLENGES FOR THE HYPOTHESIS

In human studies, there are practical difficulties involved with measuring POPs in the blood, including high costs and complex assays. As the serum concentrations of POPs are continuously affected by weight loss and gain, prospective studies may require serial measurements of POPs. In in-vitro and in-vivo experimental studies, how to simulate the exposure dose, duration, and mixture patterns in humans would be critical.

LINKAGE TO OTHER MAJOR THEORIES

Even though POPs are direct neurotoxins at a high dosage, low-dose POPs are mitochondrial toxins. Therefore, chronic exposure to low-dose POPs is linked to known key interrelated mechanisms in the pathogenesis of dementia, such as mitochondrial dysfunction and neuroinflammation.

The Effect of Combined Aerobic Exercise and Calorie Restriction on Mood, Cognition, and Motor Behavior in Overweight and Obese Women

BACKGROUND

The benefits of weight loss programs on mood, cognitive, and motor behavior are largely limited to those of calorie restriction or exercise alone. Our aim was to investigate the effect of combined calorie restriction and aerobic exercise intervention on mood, brain activity, and cognitive and motor behavior in overweight and obese women.

METHODS

Participants aged 36-56 years were randomized to either a control or an experimental group (aerobic exercise + 12.5% energy intake reduction) for a 6-month period. Changes in brain-derived neurotrophic factor levels, mood, prefrontal cortex activity, cognitive and motor performance were assessed.

RESULTS

Confusion and depression increased in the control group (P < .05), whereas tension decreased in the experimental group (P < .05). Brain-derived neurotrophic factor level and learning of a speed-accuracy task remained unchanged. Although prefrontal cortex activity and executive functions were not affected, the reaction time of visual scanning and associative learning were improved in the experimental group (P < .05). An improvement in reaction time during the speed-accuracy task was observed (P < .05).

CONCLUSION

Combined calorie restriction and aerobic exercise intervention improved the psychosocial state, had little impact on cognition, and no effect on brain activity and learning of the speed-accuracy task.

Overlapping mechanisms linking insulin resistance with cognition and neuroprogression in bipolar disorder

Cognitive impairment is highly prevalent in the progression of both diabetes mellitus and bipolar disorder. The relationship between insulin resistance in diabetes and the risk of developing major neurocognitive disorders such as Alzheimer's disease has been well described. Insulin resistance and the associated metabolic deficiencies lead to biochemical alteration which hasten neurodegeneration and subsequent cognitive impairment. For bipolar disorder, some patients experience a cyclical, yet progressive course of illness. These patients are also more likely to have medical comorbidities such as cardiovascular disease and diabetes, and insulin resistance in particular may precede the neuroprogressive course. Diabetes and bipolar disorder share epidemiological, biochemical, and structural signatures, as well as cognitive impairment within similar domains, suggesting a common mechanism between the two conditions. Here we describe the association between insulin resistance and cognitive changes in bipolar disorder, as well as potential implications for therapeutic modulation of neuroprogression.

Bariatric Surgery and Brain Health-A Longitudinal Observational Study Investigating the Effect of Surgery on Cognitive Function and Gray Matter Volume

Dietary modifications leading to weight loss have been suggested as a means to improve brain health. In morbid obesity, bariatric surgery (BARS)-including different procedures, such as vertical sleeve gastrectomy (VSG), gastric banding (GB), or Roux-en-Y gastric bypass (RYGB) surgery-is performed to induce rapid weight loss. Combining reduced food intake and malabsorption of nutrients, RYGB might be most effective, but requires life-long follow-up treatment. Here, we tested 40 patients before and six months after surgery (BARS group) using a neuropsychological test battery and compared them with a waiting list control group. Subsamples of both groups underwent structural MRI and were examined for differences between surgical procedures. No substantial differences between BARS and control group emerged with regard to cognition. However, larger gray matter volume in fronto-temporal brain areas accompanied by smaller volume in the ventral striatum was seen in the BARS group compared to controls. RYGB patients compared to patients with restrictive treatment alone (VSG/GB) had higher weight loss, but did not benefit more in cognitive outcomes. In sum, the data of our study suggest that BARS might lead to brain structure reorganization at long-term follow-up, while the type of surgical procedure does not differentially modulate cognitive performance.

Metabolic Syndrome and Cognitive Functions in Schizophrenia-Implementation of Dietary Intervention

INTRODUCTION

The co-existence of schizophrenia and metabolic syndrome is a widely described phenomenon that contributes to the worse functioning of patients in everyday life. A relatively new area of research is the relationship between metabolic syndrome (MS) and cognitive function in patients with schizophrenia. The aim of the study was to verify the relationship between the presence of metabolic syndrome and cognitive function of patients with schizophrenia and to assess the possibility of changing cognitive function by introducing appropriate dietary intervention.

MATERIALS AND METHODS

The study involved 87 individuals diagnosed with schizophrenia according to ICD-10 criteria, aged 19 to 67 years (M = 41.67; SD = 11.87). Patients were in the remission phase of schizophrenia, all using antipsychotics for pharmacological treatment. From a group of 83 patients with schizophrenia and diagnosed metabolic syndrome (according to IDF criteria) 30 patients were randomly assigned to an experimental group-with dietary intervention, 29 patients-to group without dietary intervention, 24 patients with schizophrenia without metabolic syndrome was a comparison group. All groups were evaluated for cognitive function using Stroop Test, Trail Making Test (TMT), Verbal Fluency Test, Digit Span Backwards Test. In the experimental group a dietary intervention was applied, which was to provide the examined person with a 7-day dietary plan with reduced calorie content, in compliance with the Mediterranean diet.

RESULTS

After the dietary intervention there was a significant improvement in the number of errors made in the third Stroop Test (p <0.001), the time taken to complete the Point Linking Test was shortened (Test B; p = 0.005), there was an improvement in Verbal Fluency Test in "animals" category (p = 0.006) "sharp objects" category (p = 0.009), the number of repeated digits has increased in Digit Span Test in "forward" category (p = 0.001) and overall completion of the test (p = 0.021). In the group of patients with MS without dietary intervention, the results of cognitive tests remained mostly unchanged.

CONCLUSIONS

Change of eating habits may be a significant element of a holistic approach to the problems of treatment of schizophrenia.

Pathways of Prevention: A Scoping Review of Dietary and Exercise Interventions for Neurocognition

Alzheimer's disease and related dementias (ADRD) represent an increasingly urgent public health concern, with an increasing number of baby boomers now at risk. Due to a lack of efficacious therapies among symptomatic older adults, an increasing emphasis has been placed on preventive measures that can curb or even prevent ADRD development among middle-aged adults. Lifestyle modification using aerobic exercise and dietary modification represents one of the primary treatment modalities used to mitigate ADRD risk, with an increasing number of trials demonstrating that exercise and dietary change, individually and together, improve neurocognitive performance among middle-aged and older adults. Despite several optimistic findings, examination of treatment changes across lifestyle interventions reveals a variable pattern of improvements, with large individual differences across trials. The present review attempts to synthesize available literature linking lifestyle modification to neurocognitive changes, outline putative mechanisms of treatment improvement, and discuss discrepant trial findings. In addition, previous mechanistic assumptions linking lifestyle to neurocognition are discussed, with a focus on potential solutions to improve our understanding of individual neurocognitive differences in response to lifestyle modification. Specific recommendations include integration of contemporary causal inference approaches for analyzing parallel mechanistic pathways and treatment-exposure interactions. Methodological recommendations include trial multiphase optimization strategy (MOST) design approaches that leverage individual differences for improved treatment outcomes.

Neuroimaging correlates of cognitive changes after bariatric surgery

BACKGROUND

Obesity has been associated with cognitive deficits and increased risk for developing dementia. Bariatric surgery may result in improved cognitive function; however, the underlying structural and functional brain correlates are unclear.

OBJECTIVES

This longitudinal study explores the hypothesis that specific brain regions and networks underlie cognitive changes after bariatric surgery.

SETTING

University Hospital, United States.

METHODS

Seventeen patients were recruited for this prospective cohort study, including 9 patients undergoing bariatric surgery, and 8 age-, sex-, and education level-matched healthy, nonobese control patients. Bariatric patients underwent longitudinal neuropsychologic tests and magnetic resonance imaging (MRI) scans both before and 6 months after surgery. One patient was lost to follow-up. The same neuropsychologic tests and MRI scans were performed for control patients. Differences in MRI and neuropsychologic testing between bariatric patients and control patients, and longitudinal changes within bariatric patients were assessed.

RESULTS

At baseline, bariatric patients demonstrated deficits in cognitive function relative to control patients, including pattern comparison (P = .009) and picture sequence memory (P = .004), which improved after significant weight loss. Baseline cognitive deficits in bariatric patients were accompanied by significantly lower left executive control network connectivity on resting-state functional MRI relative to control patients (P = .028), but differences resolved or diminished after bariatric surgery. Longitudinal improvements in pattern comparison performance correlated significantly with increases in left executive control network connectivity (r = .819; P = .013). No significant group or longitudinal differences were found in brain perfusion or brain white matter lesions.

CONCLUSIONS

Individuals with obesity undergoing bariatric surgery exhibit deficits in cognitive function and specific alterations of brain networks; however, cognitive performance can improve, and executive control network connectivity can increase after weight loss from bariatric surgery.

Impact of a Multidomain Intensive Lifestyle Intervention on Complaints About Memory, Problem-Solving, and Decision-Making Abilities: The Action for Health in Diabetes Randomized Controlled Clinical Trial

Background

Lifestyle interventions to reduce weight and increase activity may preserve higher-order cognitive abilities in overweight/obese adults with type 2 diabetes (T2D).

Methods

Adults (N = 5,084) with T2D who enrolled in a randomized clinical trial of a 10-year intensive lifestyle intervention (ILI) compared with diabetes support and education were queried at baseline and repeatedly during follow-up for complaints about difficulties in memory, problem-solving, and decision-making abilities.

Results

For those without baseline complaints, assignment to ILI was associated with lower odds that complaints would emerge during follow-up for decision-making ability (odds ratio [OR]=0.851, [95% CI, 0.748,0.967], p=0.014), and, among individuals who were not obese, lower odds that complaints would emerge about problem-solving ability (OR=0.694 [0.510,0.946]). No cognitive benefits from ILI were seen for individuals with baseline complaints about cognitive abilities. ILI may have exacerbated the severity of complaints about problem-solving ability during follow-up among individuals with baseline complaints and cardiovascular disease (OR=2.949 [1.378,6.311]).

Conclusions

A long-term multidomain ILI may reduce the likelihood that complaints about difficulties in higher-order cognitive abilities will emerge in T2D adults without pre-existing complaints. Among those with pre-existing complaints, the ILI did not prevent increases in complaint severity.

Relationship of metabolic syndrome and neurocognitive deficits in patients with schizophrenia

This study aimed to evaluate the association of the metabolic syndrome (MS) and its components with neurocognition among patients with schizophrenia. 121 patients with schizophrenia from an outpatient service of two psychiatric centers were assessed on a neurocognitive battery and by metabolic measures. More than half (56.2%) of the patients fulfilled the consensus criteria for MS. After controlling/adjusting for various covariates (age, education in years, duration of illness, age of onset, Positive and Negative Symptom scale score and presence of smoking status), it was found that compared to patients without MS, those with MS had significantly poorer performance "in the cognitive domains" of cognitive processing and selective attention (Stroop effect percentile; p value 0.002; effect size-0.45) and auditory and verbal memory (AVLT; p value <0.001; effect size 0.68). Patients with a higher number of abnormal parameters of MS had poorer functioning in the domains of cognitive processing and selective attention, auditory and verbal memory, and executive tasks. To conclude, this two center study suggests that MS has a negative impact on neurocognition in patients with schizophrenia. There is a need to identify and monitor metabolic abnormalities among patients with schizophrenia to minimize the negative effect of metabolic parameters on neurocognition.