To be obese--does it matter if you are metabolically healthy?

From Beats to Metabolism: the Heart at the Core of Interorgan Metabolic Cross Talk

The heart, once considered a mere blood pump, is now recognized as a multifunctional metabolic and endocrine organ. Its function is tightly regulated by various metabolic processes, at the same time it serves as an endocrine organ, secreting bioactive molecules that impact systemic metabolism. In recent years, research has shed light on the intricate interplay between the heart and other metabolic organs, such as adipose tissue, liver, and skeletal muscle. The metabolic flexibility of the heart and its ability to switch between different energy substrates play a crucial role in maintaining cardiac function and overall metabolic homeostasis. Gaining a comprehensive understanding of how metabolic disorders disrupt cardiac metabolism is crucial, as it plays a pivotal role in the development and progression of cardiac diseases. The emerging understanding of the heart as a metabolic and endocrine organ highlights its essential contribution to whole body metabolic regulation and offers new insights into the pathogenesis of metabolic diseases, such as obesity, diabetes, and cardiovascular disorders. In this review, we provide an in-depth exploration of the heart's metabolic and endocrine functions, emphasizing its role in systemic metabolism and the interplay between the heart and other metabolic organs. Furthermore, emerging evidence suggests a correlation between heart disease and other conditions such as aging and cancer, indicating that the metabolic dysfunction observed in these conditions may share common underlying mechanisms. By unraveling the complex mechanisms underlying cardiac metabolism, we aim to contribute to the development of novel therapeutic strategies for metabolic diseases and improve overall cardiovascular health.

Obesity and Metabolic Dysregulation in Children Provide Protective Influenza Vaccine Responses

The most effective intervention for influenza prevention is vaccination. However, there are conflicting data on influenza vaccine antibody responses in obese children. Cardio-metabolic parameters such as waist circumference, cholesterol, insulin sensitivity, and blood pressure are used to subdivide individuals with overweight or obese BMI into ‘healthy’ (MHOO) or ‘unhealthy’ (MUOO) metabolic phenotypes. The ever-evolving metabolic phenotypes in children may be elucidated by using vaccine stimulation to characterize cytokine responses. We conducted a prospective cohort study evaluating influenza vaccine responses in children. Participants were identified as either normal-weight children (NWC) or overweight/obese using BMI. Children with obesity were then characterized using metabolic health metrics. These metrics consisted of changes in serum cytokine and chemokine concentrations measured via multiplex assay at baseline and repeated at one month following vaccination. Changes in NWC, MHOO and MUOO were compared using Chi-square/Fisher’s exact test for antibody responses and Kruskal–Wallis test for cytokines. Differences in influenza antibody responses in normal, MHOO and MUOO children were statistically indistinguishable. IL-13 was decreased in MUOO children compared to NWC and MHOO children (p = 0.04). IL-10 approached a statistically significant decrease in MUOO compared to MHOO and NWC (p = 0.07). Influenza vaccination does not provoke different responses in NCW, MHOO, or MUOO children, suggesting that obesity, whether metabolically healthy or unhealthy, does not alter the efficacy of vaccination. IL-13 levels in MUO children were significantly different from levels in normal and MHOO children, indicating that the metabolically unhealthy phenotypes may be associated with an altered inflammatory response. A larger sample size with greater numbers of metabolically unhealthy children may lend more insight into the relationship of chronic inflammation secondary to obesity with vaccine immunity.

Changes in Body Composition Are Associated with Metabolic Changes and the Risk of Metabolic Syndrome

In a cohort of 190,599 participants from The National Health Insurance Service-National Health Screening (NHIS-HEALS) study, we investigated the association of changes in the predicted body composition and metabolic profiles with the risk of metabolic syndrome (MetS) in the general population, which was hitherto incompletely elucidated. At baseline and follow-up examinations, the body composition, including lean body mass (LBM), body fat mass (BFM), and appendicular skeletal mass (ASM), were estimated using a prediction equation, and the risk of MetS was analyzed according to relative body composition changes. An increase in relative LBM and ASM decreased the risk of MetS in men and women (adjusted odds ratio (aOR), 0.78 and 0.80; 95% confidence interval (CI), 0.77-0.79 and 0.79-0.81, respectively; all p < 0.001). As relative LBM and ASM increased, the risk of MetS was more significantly reduced in the group with higher baseline BMI and body fat mass index (BFMI)(all p-trend < 0.001). In men, when the relative LBM increased (aOR, 0.68; 95% CI, 0.63-0.73), the risk of MetS was low despite increased BMI. Thus, our findings suggested that an increase in the relative LBM and ASM reduced the risk of MetS, whereas an increase in the relative BFMI increased the risk of MetS; this result was consistent in men despite an increase in BMI.

Age-dependent effect of metabolic phenotypes on carotid atherosclerotic disease in coronary heart disease patients (CORDIOPREV study)

Background

Aging is associated with a high risk for cardiovascular disease. The relation of obesity and risk of cardiovascular events appears to be more closely linked to certain clinical or metabolic phenotypes than to obesity itself. Our aim was to establish whether aging influenced the metabolic phenotypes regarding to cardiovascular risk, evaluated by changes in the intima media thickness-common carotid (IMT-CC), in coronary heart disease (CHD) patients.

Methods

In this cross-sectional study, 1002 CHD patients were studied at entry from the CORDIOPREV study. We performed carotid ultrasound assessment to obtain their IMT-CC values. Carotid atherosclerosis was considered to exist if IMT-CC > 0.7 mm.

Results

Age determined a higher IMT-CC, regardless metabolic phenotype (all p < 0.05). Metabolically healthy non-obese (MHNO) aged< 60 showed a lesser prevalence for carotid atherosclerotic disease than metabolically sick non-obese (MSNO) and obese (MSO), while MHNO aged≥60 only showed less prevalence for the disease than the MSO. Carotid atherosclerosis associated with age, sex, impaired fasting glucose (IFG), hypertension and high sensitivity C-reactive protein (hsCRP). However, in patients aged< 60, it associated with sex and IFG and in the age ≥ 60 group, with hypertension and hsCRP.

Conclusions

Our results suggest that CHD patients aged≥60 are less metabolic flexible compared to patients aged< 60. Thus, MHO patients aged≥60 show the same risk of suffering carotid atherosclerosis as those with metabolic disease, while MHO patients aged< 60 show lower risk than MSO. This fact indicates the need to focus on therapeutic strategies in order to modify those parameters related to obesity and metabolic inflexibility in patients with CHD before entering old age.

Metabolically Healthy Obesity-Heterogeneity in Definitions and Unconventional Factors

The concept of heterogeneity among obese individuals in their risk for developing metabolic dysfunction and associated complications has been recognized for decades. At the origin of the heterogeneity idea is the acknowledgement that individuals with central obesity are more prone to developing type 2 diabetes and cardiovascular disease than those with peripheral obesity. There have been attempts to categorize subjects according to their metabolic health and degree of obesity giving rise to different obese and non-obese phenotypes that include metabolically unhealthy normal-weight (MUHNW), metabolically healthy obese (MHO), and metabolically unhealthy obese (MUO). Individuals belonging to the MHO phenotype are obese according to their body mass index although exhibiting fewer or none metabolic anomalies such as type 2 diabetes, dyslipidemia, hypertension, and/or unfavorable inflammatory and fribinolytic profiles. However, some authors claim that MHO is only transient in nature. Additionally, the phenotype categorization is controversial as it lacks standardized definitions possibly blurring the distinction between obesity phenotypes and confounding the associations with health outcomes. To add to the discussion, the factors underlying the origin or protection from metabolic deterioration and cardiometabolic risk for these subclasses are being intensely investigated and several hypotheses have been put forward. In the present review, we compare the different definitions of obesity phenotypes and present several possible factors underlying them (adipose tissue distribution and cellularity, contaminant accumulation on the adipose tissue, dysbiosis and metabolic endotoxemia imposing on to the endocannabinoid tone and inflammasome, and nutrient intake and dietary patterns) having inflammatory activation at the center.

Chronic medical conditions based obesity phenotypes: A two-step cluster analysis of a representative sample of obese American adults

BACKGROUND AND OBJECTIVE

Although obesity is a heterogeneous disease, little is known regarding chronic medical conditions (CMCs) that defines variability in obese populations. The characterization of obese populations using CMCs rather than categorization using BMI alone can advance understanding of obesity. The aims of this study are to phenotype obesity in a large representative sample of non-Hispanic White (NHW), non-Hispanic Black (NHB) and Mexican American (MA) obese adults using CMCs, and assess relationship between resulting phenotypes and self-rated health (SRH).

METHODS

Sex-specific two-step cluster analysis was used to phenotype obese participants (n = 12,547) to CMC-based clusters. The prevalence of CMCs and lifestyle risk factors in each cluster was assessed. Sex and race/ethnic specific association between cluster membership and SRH was determined using odds ratio (OR) from logistic regression analysis.

RESULTS

Distinct subgroups of obese men and women were observed: moderate dyslipidemic healthy young obese men, hypertensive-dyslipidemic middle-age obese men, hypertensive young obese men, hypertensive-dyslipidemic-asthmatic middle-age obese men, and syndemic elderly obese men, healthy young obese women, hypertensive-dyslipidemic middle-age obese women, dyslipidemic young adult obese women, syndemic middle-age obese women, and syndemic elderly obese women. Participants in the more CMCs symptomatic clusters reported high rates of behavioral risk factors and showed significantly greater odds of poor SRH than participants in the less symptomatic clusters. Compared to obese persons who are asymptomatic for CMCs, syndemic elderly obese and women men had much higher increased ORs for poor SRH with values of 3.88 [95% CI = 2.41-6.26], 3.96 [95% CI = 1.86-8.30] and 7.25 [95% CI = 2.41-9.6] for NHW, NHB and MA men, respectively. The corresponding ORs for women are 4.08 [95% CI = 2.71-6.14], 4.01 [95% CI = 2.40-6.69], and 2.62 [95% CI = 1.32-5.19], respectively.

CONCLUSION

Obesity treatment and intervention should consider heterogeneity within obese persons and pay greater attention to obesity related co-morbidities and metabolic manifestations.

Duration and stability of metabolically healthy obesity over 30 years

BACKGROUND

Obese adults who are free from metabolic risk factors may develop risk factors over time. Our objective was to characterize development of obesity and duration of metabolically healthy obese (MHO) over 30 years.

METHODS

Participants in CARDIA who developed obesity (BMI ≥ 30 kg/m2) at follow-up exams during years 7, 10, 15, 20, 25, and 30 were analyzed. MHO was defined as obese and having 0 or 1 risk factor: ≥SBP/DBP 130/85 mmHg; fasting glucose ≥100 mg/dL/5.55 mmol/L; fasting triglycerides (≥150 mg/dL/1.69 mmol/L); and HDL-C (men <40 mg/dL/1.036 mmol/L, women <50 mg/dL/1.295 mmol/L) or on any medication(s) for these conditions. MHO duration (years) and obesity duration (years) were estimated for each subsequent time-point; and an overall cumulative duration was also calculated over available follow-up. MHO duration (%) was approximated as MHO duration ÷ obesity duration. Stable MHO was defined as 100% MHO duration over follow-up, while transient MHO was defined as <1-99%. Chi-squared tests were used to compare proportions by sex and race across obesity phenotypes. Multivariable-adjusted ANCOVA, adjusting for baseline BMI, age, race, and sex, was used to analyze obesity duration in all individuals who developed obesity, and also compare MHO duration (%) across race and sex in transient MHO individuals.

RESULTS

Of the 987 eligible participants who developed obesity, 51% were African American (AA), 56% were women. Higher percentages of AA were classified as transient MHO, and higher proportions of females were MHO (both p < 0.0001). Obesity duration (years) was higher in transient MHO compared with stable MHO (mean difference: 6.2 ± 0.5 years, p < 0.0001). Of those with transient MHO, African Americans (51.4 ± 1.6%) were more likely to have longer MHO duration compared to Caucasians (44.4 ± 1.9%, p = 0.005).

CONCLUSION

MHO status can be a transient phenotype which differs by sex and race. Future studies are needed to explore modifiable lifestyle/behavioral predictors associated with longer MHO duration.

Risk of hypertension among different metabolic phenotypes: a systematic review and meta-analysis of prospective cohort studies

We performed a meta-analysis to assess the association of body mass index (BMI) and metabolic status with the risk of incident hypertension. Relevant studies were identified by searching comprehensive search via PubMed and Scopus search engines up to May 2018 and were analyzed using a random-effects model. Eight prospective studies were included in the analyses with metabolically healthy normal weight (MHNW) as the reference group. Pooled relative risks (RRs) and their 95% confidence intervals (CI) were calculated using random-effects or fixed-effect models when appropriate. Subgroup analysis was applied to define possible sources of heterogeneity. Overall, among 79090 participants, the risk of hypertension in metabolically unhealthy obese (MUHO) and metabolically healthy obese phenotypes (MHO) increased compared with the reference group (pooled effect size = 1.95, 95%CI: 1.87-2.04, P < 0.001 vs pooled effect size: 1.54, 95%CI: 1.48-1.61, P < 0.001, respectively). Also, a significant positive association between metabolically unhealthy normal weight (MUHNW) phenotype and the risk of hypertension was observed (pooled effect size = 1.48, 95%CI: 1.41-1.55, P < 0.001). Metabolically unhealthy overweight (MUHOW) and metabolically healthy overweight (MHOW) phenotypes had greater risk of hypertension compared with the MHNW phenotype (pooled effect size = 1.50, 95%CI: 1.13-1.71, P < 0.001 and pooled effect size = 1.18, 95%CI: 1.11-1.27, P < 0.001). This meta-analysis revealed that individuals with metabolic abnormality had a higher risk for hypertension and also suggests that MHOW/ MHO are not a benign condition. We are refuting the notion that overweight and obesity without metabolic abnormalities are benign conditions in all population.

Body composition analysis and references in children: clinical usefulness and limitations

The prevalence of obesity is increasing over the world. Especially in Asians compared to Caucasians, there has been a significant increase in the population with major chronic diseases. This has developed over a shorter time period which is associated with socioeconomic changes in recent decades and a greater predisposition to cardiometabolic disorders. Many Asians could be classified has having normal weight but with obesity as evidenced by body composition (BC) and fat distribution. Overweight in Asian adults is classified as a BMI > 23 kg/m² and obesity as a BMI > 25 kg/m². An effective strategy to manage the obesity epidemic by focusing on childhood obesity is needed because of the huge impact that obesity exerts on population health. However, monitoring tools are limited to anthropometry such as BMI and BMI z-scores which define overweight and obese as a BMI exceeding the 85th and 95th percentiles, respectively, on reference growth charts. To overcome the limitations of BMI, reference values for BC components have been produced using various techniques. The use of BC charts for children in personalized therapeutic approach has increased, although there is a lack of a consensus on a single reference technique. Zones on BC charts and the personalized values of BC components could be practical, especially for the detection of metabolically unhealthy normal weight (MUN) children. BC charts should be included in the growth chart package and BC monitoring through the entire life course will help us understand the association between growth, aging, health and disease.

All-cause mortality of metabolically healthy or unhealthy obese: risk stratification using myocardial perfusion imaging

Introduction

There is still controversy about the favorable prognosis of "metabolically healthy" (MH) obese. This study evaluated mortality and the use of myocardial perfusion scintigraphy (MPS) for risk stratification of MH or metabolically unhealthy (MU) obese or nonobese patients.

Material and methods

Patients without dyslipidemia, hypertension, or diabetes were considered MH, and those with ≥ 1 of these risk factors were considered MU. The MPS was categorized as normal, abnormal or ischemic. Patients were followed for 4.0 ±1.0 years for all-cause death.

Results

Of 2450 patients, 613 were obese. The MH obese patients less often had ischemia than MU obese, but there was no significant difference in the prevalence of ischemia compared to all nonobese. The annualized death rate of MH obese was 1.3% and of nonobese 1.0% (p = 0.4). An abnormal MPS and the MU status were independently associated with death, with hazard ratios of 1.85 and 1.72, respectively. A normal MPS identified patients with low risk among all subgroups; annualized rates of death were 1.0%, 1.1% and 1.0% for all nonobese, MH obese and MU obese, respectively (p = 0.63).

Conclusions

The annualized death rate of MH obese patients was not significantly different from that of nonobese individuals. Myocardial perfusion scintigraphy was able to stratify prognosis in the overall patient population. These data may be helpful to identify high-risk individuals, thereby improving patient management.

Association between metabolic syndrome and gingival inflammation in obese children

BACKGROUND AND OBJECTIVE

Our previous work showed a positive association between metabolic syndrome (MetS) and gingival crevicular fluid (GCF) tumour necrosis factor-alpha (TNF-α) in a sample of obese and non-obese children. However, whether this association persists among obese children is unknown. We aim to investigate the extent to which MetS is associated with GCF TNF-α level among obese children.

METHODOLOGY

We performed a cross-sectional analysis using data from visit 1 of the QUebec Adipose and Lifestyle InvesTigation in Youth cohort. A total of 219 obese children aged 8-10 years, for whom data were available for both MetS and TNF-α, were included in our analysis. The independent variable, MetS, was defined according to the International Diabetes Federation recommendations. GCF samples were collected from the gingival sulcus using a paper strip, and the concentration of TNF-α was determined by enzyme-linked immunosorbent assay. Analyses included descriptive statistics and sex-specific linear regression analyses adjusting for potential confounders.

RESULTS

In this sample comprising only obese children, 24 (10.9%) had MetS. Among obese boys, those with MetS had 44.9% higher GCF TNF-α (95% confidence interval: 16.5%-73.3%) compared to those without MetS. No such association was detected in obese girls.

CONCLUSION

MetS was positively associated with GCF TNF-α concentration in obese boys. These results suggest that obese boys with MetS may have a worse gingival health profile compared to their obese counterpart without MetS.

Body fat distribution, in particular visceral fat, is associated with cardiometabolic risk factors in obese women

BACKGROUND

Body fat distribution is, next to overall obesity, an important risk factor for cardiometabolic outcomes in the general population. In particular, visceral adipose tissue (VAT) is strongly associated with cardiometabolic risk factors. Since it is unclear whether body fat distribution is also important in men and women with obesity we investigated the associations between measures of body fat distribution and cardiometabolic risk factors in men and women with obesity.

METHODS

In this cross-sectional analysis of obese men and women (BMI≥30 kg/m2) included in the Netherlands Epidemiology of Obesity Study, waist:hip ratio(WHR), waist circumference, and MRI-based abdominal subcutaneous adipose tissue (aSAT) and VAT were determined. Associations between measures of body fat distribution and presence of ≥1 risk factor, such as hypertension or hypertriglyceridemia, were examined using logistic regression analyses; stratified by sex and adjusted for age, ethnicity, education, tobacco smoking, alcohol consumption, physical activity and depending on the association additionally for total body fat or VAT.

RESULTS

We included 2,983 obese individuals (57% women) with a mean age of 56 and standard deviation (SD) of 6 and mean BMI of 34.0 kg/m2 (4.0), after exclusion of individuals with missing values of cardiometabolic risk factors (n = 33). 241 individuals were obese without other cardiometabolic risk factors. In obese women, all measures of body fat distribution except aSAT (OR per SD:0.76, 95%CI: 0.53, 1.10) were associated with having ≥1 cardiometabolic risk factor, of which VAT most strongly associated (5.77; 3.02, 11.01). In obese men, associations of body fat distribution and the presence of cardiometabolic risk factors were attenuated. (e.g. VAT:1.42; 0.84, 2.41).

CONCLUSIONS

In obese women, but less so in men, measures of body fat distribution, of which VAT most strongly, are associated with cardiometabolic risk factors.

The influence of physical activity on risk of cardiovascular disease in people who are obese but metabolically healthy

The metabolic outcomes of metabolically healthy obesity (MHO) remain controversial. The aim of the present study was to determine the effect of physical activity on the cardiovascular disease (CVD) outcomes of MHO. The study included participants who were followed for 10 years and recruited from the Korean Genome and Epidemiology Study (KoGES), a population-based cohort study. Participants with previously recorded CVDs or cancer, or who had received steroids or anticoagulants at baseline were excluded. A total of 8144 participants (3,942 men and 4,202 women) fulfilled inclusion criteria. In a multivariate Cox regression model adjusted for age and sex, MHO participants were not at elevated risk of CVD compared with their metabolically healthy non-obese (MHNO) counterparts (HR, 1.28; 95% CI, 0.96–1.71), although both the non-obese (HR, 1.50; 95% CI, 1.19–1.90) and obese (HR, 1.85; 95% CI, 1.48–2.30) participants with metabolic abnormalities were at elevated risk. However, in the subgroup analysis by physical activity, physically inactive MHO participants had a significantly higher HR for CVD events compared to active MHNO participants (HR, 1.54; 95% CI, 1.03–2.30), while active MHO participants were not at elevated risk (HR, 1.15; 95% CI, 0.70–1.89). Physically inactive MHO participants had significantly increased risk of CVD compared to physically active MHNO participants whereas physically active MHO participants did not.

Change in Body Weight from Age 20 Years Is a Powerful Determinant of the Metabolic Syndrome

BACKGROUND

Higher body weight is a well-known determinant of the metabolic syndrome (MetS) and its components. It is however less well studied how the change in weight from age 20 years to middle age or old age affects MetS development.

METHODS

In the community-based EpiHealth (n = 19,000, age range 45 to 75 years, 56% females) and PIVUS (n = 1000, all aged 70 years, 50% females) studies, the participants were asked about their body weight at age 20 years. Data were collected to determine MetS prevalence (NCEP ATP III criteria).

RESULTS

In EpiHealth, the probability of having MetS increased fairly linearly with increasing weight from age 20 in the obese [odds ratios (OR) 1.04 per kg change in weight, 95% confidence interval (CI) 1.03-1.05, P < 0.0001], as well as in the overweight (OR 1.15, 95% CI 1.14-1.17, P < 0.0001) and normal-weight (OR 1.18, 95% CI 1.14-1.21, P < 0.0001), subjects after adjustment for age, sex, body mass index (BMI) at age 20, alcohol intake, smoking, education, and exercise habits. Also in the PIVUS study, the change in weight over 50 years was related to prevalent MetS (OR 1.08 per kg change in weight, 95% CI 1.06-1.10, P < 0.0001). In both studies, self-reported BMI at age 20 was related to prevalent MetS.

CONCLUSION

Self-reported weight gain from age 20 was strongly and independently associated with prevalent MetS both in middle age or old age. Interestingly, this relationship was not restricted only to obese subjects. Our data provide additional support for the importance of maintaining a stable weight throughout life.

Complex relationship of obesity and obesity paradox in heart failure - higher risk of developing heart failure and better outcomes in established heart failure

Heart failure (HF) and obesity are major public health problems. Studies have shown that obesity may increase the risk of developing new HF but after patients have developed HF, obesity may be associated with improved outcomes. This paradoxical association of obesity with HF remains poorly understood. It is believed that the obesity paradox may in part be due to the inherent limitations of body mass index (BMI) as a measure of obesity. BMI may not appropriately measure important components of body mass like body fat, fat distribution, lean body mass, and body fluid content and may not be ideal for examining the relationship of body composition with health outcomes. Differentiating between body fat and lean body mass may explain some of the paradoxical association between higher BMI and better prognosis in patients with HF. Paradoxical outcomes in HF may also be due to phenotypes of obesity. Future studies need to develop and test metrics that may better measure body composition and may serve as a better tool for the estimation of the true association of obesity and outcomes in HF and determine whether the association may vary by obesity phenotypes. KEY MESSAGES Obesity predisposes to heart failure in all age groups. But obesity in heart failure is an area of controversy, because of obesity paradox, the apparent protective effect of overweight and mild obesity on mortality after development of heart failure. Traditional markers of obesity do not measure different components of body weight like muscle mass, fat, water, and skeletal weight. Body Mass Index in heart failure subjects does not measure accurately body fat or fluid retention. So new markers of obesity like visceral adiposity index, body composition analysis, sarcopenic status assessment may be helpful in the assessment of heart failure outcomes. Different phenotypes of obesity may be responsible for the different morbidity, mortality as well as therapeutic outcomes in heart failure.

"Metabolically healthy" obesity: Prevalence, clinical features and association with myocardial ischaemia

OBJECTIVE

To evaluate the prevalence of the "metabolically healthy" (MH) or "metabolically unhealthy" (MU) obesity phenotypes and their association with cardiorespiratory fitness and inducible myocardial ischaemia.

METHODS

Individuals without known coronary artery disease undergoing myocardial perfusion single-photon emission computed tomography (MPS) were studied. Those without dyslipidemia, hypertension, or diabetes were considered MH, and when ≥1 of these was present, MU status was considered present. Summed stress and difference perfusion scores (SSS and SDS, respectively) were calculated; a SDS >1 defined ischaemic MPS.

RESULTS

MH patients were 35.0% of the nonobese population and 23.5% of the obese (p<0.001). The prevalence of ischaemia was not significantly different between MH patients with obesity or MH patients without obesity (10.9% vs 9.1%, p=0.3), except for patients with body mass index ≥40kg/m² (21.9%). MH obese patients were less frequently able to exercise and had lower exercise capacity than the nonobese patients.

CONCLUSIONS

The prevalence of myocardial ischaemia was not significantly different between MH obese or nonobese individuals, supporting the concept of the "metabolically healthy obesity". However, there are other factors involved, such as the ability to exercise, that influence the risk of myocardial ischaemia, limiting the "safety" of that obesity phenotype.

Obesity and Cardiovascular Disease

The prevalence of obesity has increased worldwide over the past few decades. In 2013, the prevalence of obesity exceeded the 50% of the adult population in some countries from Oceania, North Africa, and Middle East. Lower but still alarmingly high prevalence was observed in North America (≈30%) and in Western Europe (≈20%). These figures are of serious concern because of the strong link between obesity and disease. In the present review, we summarize the current evidence on the relationship of obesity with cardiovascular disease (CVD), discussing how both the degree and the duration of obesity affect CVD. Although in the general population, obesity and, especially, severe obesity are consistently and strongly related with higher risk of CVD incidence and mortality, the one-size-fits-all approach should not be used with obesity. There are relevant factors largely affecting the CVD prognosis of obese individuals. In this context, we thoroughly discuss important concepts such as the fat-but-fit paradigm, the metabolically healthy but obese (MHO) phenotype and the obesity paradox in patients with CVD. About the MHO phenotype and its CVD prognosis, available data have provided mixed findings, what could be partially because of the adjustment or not for key confounders such as cardiorespiratory fitness, and to the lack of consensus on the MHO definition. In the present review, we propose a scientifically based harmonized definition of MHO, which will hopefully contribute to more comparable data in the future and a better understanding on the MHO subgroup and its CVD prognosis.

Invited commentary: limitations and usefulness of the metabolically healthy obesity phenotype

The fraction of the obese population who appear to be free of the metabolic abnormalities that usually accompany excess adiposity has garnered a great deal of attention recently. The so-called "metabolically healthy obesity" concept is thought to offer a refinement of the traditional obesity definitions that are based solely on anthropometry. The commentary by Rey-López et al. (Am J Epidemiol. 2015;182(9):737-741) in this issue of the Journal highlights several limitations of the "metabolically healthy obesity" concept and calls into question its usefulness as a public health metric. We discuss several of the issues raised by these authors and offer some perspective on why the utility of this concept remains unresolved.

Metabolically healthy obese individuals: Key protective factors

OBJECTIVES

Obesity is a significant quality of life-impairing health problem affecting industrialized nations. However, despite carrying a large fat mass, some very obese individuals exhibit normal metabolic profiles (metabolically healthy obesity). The physiological factors underlying their protective and favorable metabolic profiles remain poorly defined.

METHODS

A search of the National Library of Medicine PubMed database was performed using the following keywords: Metabolically healthy obese, metabolically normal obese, insulin resistance, metabolically unhealthy normal weight, and uncomplicated obesity.

RESULTS

This article reviewed factors associated with severe obesity that lacks complications, and suggests putative activities by which these obese individuals avoid developing the clinical features of metabolic syndrome, or the metabolic complications associated with severe obesity.

CONCLUSIONS

Despite the knowledge that visceral fat deposition is the seminal factor that ultimately causes insulin resistance (IR) and the detrimental inflammatory and hormonal profile that contributes to increase risk for cardiovascular disease, it remains unknown whether metabolically healthy obesity (MHO) has genetic predisposing factors, and whether MHO ultimately succumbs to IR and the metabolic syndrome, indicating a need for prophylatic bariatric surgery.

Obesity and metabolic phenotypes (metabolically healthy and unhealthy variants) are significantly associated with prevalence of elevated C-reactive protein and hepatic steatosis in a large healthy Brazilian population

BACKGROUND

Among the obese, the so-called metabolically healthy obese (MHO) phenotype is thought to confer a lower CVD risk as compared to obesity with typical associated metabolic changes. The present study aims to determine the relationship of different subtypes of obesity with inflammatory-cardiometabolic abnormalities.

METHODS

We evaluated 5,519 healthy, Brazilian subjects (43 ± 10 years, 78% males), free of known cardiovascular disease. Those with <2 metabolic risk factors (MRF) were considered metabolically healthy, and those with BMI ≥ 25 kg/m(2) and/or waist circumference meeting NCEP criteria for metabolic syndrome as overweight/obese (OW). High sensitivity C reactive protein (hsCRP) was measured to assess underlying inflammation and hepatic steatosis (HS) was determined via abdominal ultrasound.

RESULTS

Overall, 40% of OW individuals were metabolically healthy, and 12% normal-weight had ≥2 MRF. The prevalence of elevated CRP (≥3 mg/dL) and HS in MHO versus normal weight metabolically healthy group was 22% versus 12%, and 40% versus 8% respectively (P < 0.001). Both MHO individuals and metabolically unhealthy normal weight (MUNW) phenotypes were associated with elevated hsCRP and HS.

CONCLUSION

Our study suggests that MHO and MUNW phenotypes may not be benign and physicians should strive to treat individuals in these subgroups to reverse these conditions.

Metabolic and cardiovascular implications of a metabolically healthy obesity phenotype

Metabolically healthy obesity (MHO) is a new concept in which an individual may exhibit an obese phenotype in the absence of any metabolic abnormalities. There are a number of definitions of MHO that utilize a variety of components. The findings of clinical and basic studies indicate that subjects with MHO do not exhibit an increased mortality, an increased risk of cardiovascular disease, or an increased risk of type 2 diabetes mellitus, as compared to normal-weight controls. Although these findings imply that metabolic health is a more important factor than obesity, several studies have shown that subjects with MHO have a similar risk of metabolic or cardiovascular diseases as those with metabolically unhealthy obesity. Thus, there is still debate regarding not only the implications of the MHO phenotype but its very existence. Accordingly, future studies should focus on developing a unified definition of MHO and distinguishing subjects who will be at a high risk for metabolic and cardiovascular diseases.

Regulation of adipocyte lipolysis

In adipocytes the hydrolysis of TAG to produce fatty acids and glycerol under fasting conditions or times of elevated energy demands is tightly regulated by neuroendocrine signals, resulting in the activation of lipolytic enzymes. Among the classic regulators of lipolysis, adrenergic stimulation and the insulin-mediated control of lipid mobilisation are the best known. Initially, hormone-sensitive lipase (HSL) was thought to be the rate-limiting enzyme of the first lipolytic step, while we now know that adipocyte TAG lipase is the key enzyme for lipolysis initiation. Pivotal, previously unsuspected components have also been identified at the protective interface of the lipid droplet surface and in the signalling pathways that control lipolysis. Perilipin, comparative gene identification-58 (CGI-58) and other proteins of the lipid droplet surface are currently known to be key regulators of the lipolytic machinery, protecting or exposing the TAG core of the droplet to lipases. The neuroendocrine control of lipolysis is prototypically exerted by catecholaminergic stimulation and insulin-induced suppression, both of which affect cyclic AMP levels and hence the protein kinase A-mediated phosphorylation of HSL and perilipin. Interestingly, in recent decades adipose tissue has been shown to secrete a large number of adipokines, which exert direct effects on lipolysis, while adipocytes reportedly express a wide range of receptors for signals involved in lipid mobilisation. Recently recognised mediators of lipolysis include some adipokines, structural membrane proteins, atrial natriuretic peptides, AMP-activated protein kinase and mitogen-activated protein kinase. Lipolysis needs to be reanalysed from the broader perspective of its specific physiological or pathological context since basal or stimulated lipolytic rates occur under diverse conditions and by different mechanisms.

Beyond BMI: The "Metabolically healthy obese" phenotype & its association with clinical/subclinical cardiovascular disease and all-cause mortality -- a systematic review

Background

A subgroup has emerged within the obese that do not display the typical metabolic disorders associated with obesity and are hypothesized to have lower risk of complications. The purpose of this review was to analyze the literature which has examined the burden of cardiovascular disease (CVD) and all-cause mortality in the metabolically healthy obese (MHO) population.

Methods

Pubmed, Cochrane Library, and Web of Science were searched from their inception until December 2012. Studies were included which clearly defined the MHO group (using either insulin sensitivity and/or components of metabolic syndrome AND obesity) and its association with either all cause mortality, CVD mortality, incident CVD, and/or subclinical CVD.

Results

A total of 20 studies were identified; 15 cohort and 5 cross-sectional. Eight studies used the NCEP Adult Treatment Panel III definition of metabolic syndrome to define “metabolically healthy”, while another nine used insulin resistance. Seven studies assessed all-cause mortality, seven assessed CVD mortality, and nine assessed incident CVD. MHO was found to be significantly associated with all-cause mortality in two studies (30%), CVD mortality in one study (14%), and incident CVD in three studies (33%). Of the six studies which examined subclinical disease, four (67%) showed significantly higher mean common carotid artery intima media thickness (CCA-IMT), coronary artery calcium (CAC), or other subclinical CVD markers in the MHO as compared to their MHNW counterparts.

Conclusions

MHO is an important, emerging phenotype with a CVD risk between healthy, normal weight and unhealthy, obese individuals. Successful work towards a universally accepted definition of MHO would improve (and simplify) future studies and aid inter-study comparisons. Usefulness of a definition inclusive of insulin sensitivity and stricter criteria for metabolic syndrome components as well as the potential addition of markers of fatty liver and inflammation should be explored. Clinicians should be hesitant to reassure patients that the metabolically benign phenotype is safe, as increased risk cardiovascular disease and death have been shown.

Peri-conceptional obesogenic exposure induces sex-specific programming of disease susceptibilities in adult mouse offspring

Vulnerability of the fetus upon maternal obesity can potentially occur during all developmental phases. We aimed at elaborating longer-term health outcomes of fetal overnutrition during the earliest stages of development. We utilized Naval Medical Research Institute (NMRI) mice to induce pre-conceptional and gestational obesity and followed offspring outcomes in the absence of any postnatal obesogenic influences. Male adult offspring developed overweight, insulin resistance, hyperleptinemia, hyperuricemia and hepatic steatosis; all these features were not observed in females. Instead, they showed impaired fasting glucose and a reduced fat mass and adipocyte size. Influences of the interaction of maternal diet∗sex concerned offspring genes involved in fatty liver disease, lipid droplet size regulation and fat mass expansion. These data suggest that a peri-conceptional obesogenic exposure is sufficient to shape offspring gene expression patterns and health outcomes in a sex- and organ-specific manner, indicating varying developmental vulnerabilities between sexes towards metabolic disease in response to maternal overnutrition.

Favorable modulation of benign breast tissue and serum risk biomarkers is associated with > 10 % weight loss in postmenopausal women

We conducted a phase II feasibility study of a 6-month behavioral weight loss intervention in postmenopausal overweight and obese women at increased risk for breast cancer and the effects of weight loss on anthropomorphic, blood, and benign breast tissue biomarkers. 67 women were screened by random peri-areolar fine-needle aspiration, 27 were registered and 24 participated in the interventional phase. The 24 biomarker evaluable women had a median baseline BMI of 34.2 kg/m(2) and lost a median of 11 % of their initial weight. Significant tissue biomarker modulation after the 6-month intervention was noted for Ki-67 (if restricted to the 15 women with any Ki-67 at baseline, p = 0.041), adiponectin to leptin ratio (p = 0.003); and cyclin B1 (p = 0.001), phosphorylated retinoblastoma (p = 0.005), and ribosomal S6 (p = 0.004) proteins. Favorable modulation for serum markers was observed for sex hormone-binding globulin (p < 0.001), bioavailable estradiol (p < 0.001), bioavailable testosterone (p = 0.033), insulin (p = 0.018), adiponectin (p = 0.001), leptin (p < 0.001), the adiponectin to leptin ratio (p < 0.001), C-reactive protein (p = 0.002), and hepatocyte growth factor (p = 0.011). When subdivided by <10 or >10 % weight loss, change in percent total body and android (visceral) fat, physical activity, and the majority of the serum and tissue biomarkers were significantly modulated only for women with >10 % weight loss from baseline. Some factors such as serum PAI-1 and breast tissue pS2 (estrogen-inducible gene) mRNA were not significantly modulated overall but were when considering only those with >10 % weight loss. In conclusion, a median weight loss of 11 % over 6 months resulted in favorable modulation of a number of anthropomorphic, breast tissue and serum risk and mechanistic markers. Weight loss of 10 % or more should likely be the goal for breast cancer risk reduction studies in obese women.

Combined effect of obesity and cardio-metabolic abnormality on the risk of cardiovascular disease: a meta-analysis of prospective cohort studies

BACKGROUND

Cardiovascular risk is inconsistent in the normal-weight, overweight, and obese individuals due to metabolic abnormality. We aimed to investigate combined effects of obesity and metabolic abnormality on the risk of cardiovascular disease and mortality.

METHODS

The MEDLINE, EMBASE, Cochrane library, and references of relevant original articles prior to May 2013 were searched for prospective studies investigating cardiovascular risk and death associated with combined effects of obesity and metabolic syndrome or insulin resistance. Pooled relative risks (RR) and 95% confidence intervals (CI) were calculated using random-effects or fixed-effect models when appropriate.

RESULTS

Fourteen perspective studies with a total of 299,059 participants and 12,125 cases of incident CVD, 2130 cases of CVD death, and 7071 cases of all-cause death were included in the meta-analysis. Compared with healthy normal-weight individuals, metabolically healthy overweight (MHOW) and obese (MHOB) individuals showed increased risk for CVD events, which appeared much stronger during the long-term follow-up period of >15 years, with pooled RR of 1.47 (95% CI 1.37-1.58) in MHOW and 2.00 (95% CI 1.79-2.24) in MHOB. Normal-weight but metabolically abnormal individuals were at increased risk for CVD (pooled RR 1.81, 95% CI 1.56-2.10), CVD-related death (pooled RR 1.55, 95% CI 1.16-2.08), and all-cause death (pooled RR 1.27, 95% CI 1.10-1.47). Metabolically abnormal obese individuals were at the highest risk for CVD and mortality.

CONCLUSION

Individuals with metabolic abnormality, although at normal-weight, had an increased risk of CVD and mortality. Healthy overweight and obese persons had higher risk, which refuted the notion that metabolically healthy obese phenotype is a benign condition.

Abdominal fat analyzed by DEXA scan reflects visceral body fat and improves the phenotype description and the assessment of metabolic risk in mice

Clinical studies have demonstrated a strong relationship between visceral fat content and metabolic diseases, such as type 2 diabetes and liver steatosis. Obese mouse models are an excellent tool to study metabolic diseases; however, there are limited methods for the noninvasive measurement of fat distribution in mice. Although micromagnetic resonance imaging and microcomputed tomography are the "gold standards" in the measurement of fat distribution, more economical and accessible methods are required. Dual energy X-ray absorptiometry (DEXA) is an effective method in characterizing fat content; however, it cannot discriminate between visceral and subcutaneous fat depots. We demonstrate that an evaluation of abdominal fat content measured by DEXA through the selection of one localized abdominal area strongly correlates with visceral fat content in C57BL/6J mice. We found that DEXA is able to measure fat pad volume ex vivo with high accuracy; however, the measurement of visceral fat in vivo shows an overestimation caused by subcutaneous tissue interference. The overestimation is almost constant for a wide range of values, and thus it is possible to correct the data for a more accurate estimation of visceral fat content. We demonstrate the utility of this technique in characterizing phenotypes of several obese mouse models (ob/ob, db/db, MC4R-KO, and DIO) and evaluating the effect of treatments on visceral fat content in longitudinal studies. Additionally, we also establish abdominal obesity as a potential biomarker for metabolic abnormalities (liver fat accumulation, insulin resistance/diabetes) in mice, similar to that described in humans.