Effects of a lifestyle intervention in metabolically benign and malign obesity

'Adipaging': ageing and obesity share biological hallmarks related to a dysfunctional adipose tissue

The increasing ageing of our societies is accompanied by a pandemic of obesity and related cardiometabolic disorders. Progressive dysfunction of the white adipose tissue is increasingly recognized as an important hallmark of the ageing process, which in turn contributes to metabolic alterations, multi-organ damage and a systemic pro-inflammatory state ('inflammageing'). On the other hand, obesity, the paradigm of adipose tissue dysfunction, shares numerous biological similarities with the normal ageing process such as chronic inflammation and multi-system alterations. Accordingly, understanding the interplay between accelerated ageing related to obesity and adipose tissue dysfunction is critical to gain insight into the ageing process in general as well as into the pathophysiology of obesity and other related conditions. Here we postulate the concept of 'adipaging' to illustrate the common links between ageing and obesity and the fact that, to a great extent, obese adults are prematurely aged individuals.

Exercise and diabetes: relevance and causes for response variability

Exercise as a key prevention strategy for diabetes and obesity is commonly accepted and recommended throughout the world. Unfortunately, not all individuals profit to the same extent, some exhibit exercise resistance. This phenomenon of non-response to exercise is found for several endpoints, including glucose tolerance and insulin sensitivity. Since these non-responders are of notable quantity, there is the need to understand the underlying mechanisms and to identify predictors of response. This displays the basis to develop personalized training intervention regimes. In this review, we summarize the current knowledge on response variability, with focus on human studies and improvement of glucose homeostasis as outcome.

MR-based assessment of body fat distribution and characteristics

The assessment of body fat distribution and characteristics using magnetic resonance (MR) methods has recently gained significant attention as it further extends our pathophysiological understanding of diseases including obesity, metabolic syndrome, or type 2 diabetes mellitus, and allows more detailed insights into treatment response and effects of lifestyle interventions. Therefore, the purpose of this study was to review the current literature on MR-based assessment of body fat distribution and characteristics. PubMed search was performed to identify relevant studies on the assessment of body fat distribution and characteristics using MR methods. T1-, T2-weighted MR Imaging (MRI), Magnetic Resonance Spectroscopy (MRS), and chemical shift-encoding based water-fat MRI have been successfully used for the assessment of body fat distribution and characteristics. The relationship of insulin resistance and serum lipids with abdominal adipose tissue (i.e. subcutaneous and visceral adipose tissue), liver, muscle, and bone marrow fat content have been extensively investigated and may help to understand the underlying pathophysiological mechanisms and the multifaceted obese phenotype. MR methods have also been used to monitor changes of body fat distribution and characteristics after interventions (e.g. diet or physical activity) and revealed distinct, adipose tissue-specific properties. Lastly, chemical shift-encoding based water-fat MRI can detect brown adipose tissue which is currently the focus of intense research as a potential treatment target for obesity. In conclusion, MR methods reliably allow the assessment of body fat distribution and characteristics. Irrespective of the promising findings based on these MR methods the clinical usefulness remains to be established.

Cardiometabolic disease risk in metabolically healthy and unhealthy obesity: Stability of metabolic health status in adults

OBJECTIVE

To assess the stability of metabolic status and body mass index (BMI) status and their relative contribution to risk of diabetes, cardiovascular events, and mortality.

METHODS

A total of 14,685 participants from the Atherosclerosis Risk in Communities Study and 4,990 from the Coronary Artery Risk Development in Young Adults Study were included. People with healthy obesity (HO) are defined as those meeting all three indices of blood pressure, blood glucose, and blood lipids. People with unhealthy obesity crossed the risk threshold for all three criteria.

RESULTS

In both healthy and unhealthy subgroups, risks for coronary heart disease (CHD), stroke, and mortality were comparable among BMI status during a mean 18.7-year follow-up. When compared with HO, hazard ratios were increased for diabetes (5.56, 95% confidence interval [CI] 4.12-7.48), CHD (5.60, 95% CI 3.14-9.98), stroke (4.84, 95% CI 2.13-10.97), and mortality (2.6, 95% CI 1.88-3.61) in people with unhealthy obesity. BMI only moderately increased the risks for diabetes among healthy subjects. In the Coronary Artery Risk Development in Young Adults Study over 20 years, 17.5% of lean subjects and 67.3% of overweight subjects at baseline developed obesity during follow-up. Despite rising BMI, metabolic status remained relatively stable.

CONCLUSIONS

Metabolic status is relatively stable despite rising BMI. HO had lower risks for diabetes, CHD, stroke, and mortality than unhealthy subjects but increased diabetes risks than healthy lean people. Cardiometabolic risk factors confer much higher risk than obesity per se.

The Effects of a Health Partner Program on Reducing Cardiovascular Risk Factors

Previous lifestyle intervention research targeting prediabetes has primarily focused on weight loss, blood glucose, and lipid abnormalities. Far less is known whether lifestyle interventions lower other biological and physical risk factors for cardiovascular disease in overweight/obese adults with or without prediabetes. The aim of the study was to determine if a health partner program reduced biological and physical cardiovascular risk factors in overweight/obese adults with and without prediabetes at 1 year. A secondary data analysis was performed using the Center for Health Discovery and Well Being database at Emory University in the United States. A total of 246 (30 prediabetics and 216 non-prediabetics) were included in the analysis. At the 1-year follow-up, compared with non-prediabetics, prediabetics had significant improvements in body mass index, fasting blood glucose, and insulin resistance. Prediabetics also had higher increases in cardiorespiratory fitness. However, the methodological limitations and predominately high socioeconomic status level prevent definitive conclusions and generalizations.

UPDATING THE CONCEPT OF METABOLICALLY HEALTHY OBESITY

Obesity is a well-recognized risk factor for type 2 diabetes, cardiovascular disease, and several types of cancer. However, a proportion of the obese individuals display a significantly lower risk for metabolic complications than expected for their degree of body mass index, and this subtype of obesity was described as "metabolically healthy obesity" (MHO). No universally accepted criteria for the diagnosis of MHO exists and the prevalence of this subtype of obesity varies largely according to criteria used. Broadly, MHO is characterized by a lower amount of visceral fat, a more favorable inflammatory profile, and less insulin resistance as compared to the metabolically unhealthy obesity. Currently, controversies exist regarding the risk of cardiovascular events and all-cause mortality associated with MHO as compared to metabolically-healthy non-obese individuals. Further research is needed in order to identify the MHO phenotype and if MHO is truly healthy for a long period of time or if it is a transient state from normal metabolic/normal weight to abnormal metabolic/obese state. This review will discuss the MHO definition criteria; the differences between MHO and metabolically unhealthy obesity; the possible underlying mechanisms and clinical implications of MHO.

Estimation of risk for diabetes according to the metabolically healthy status stratified by degree of obesity in Korean men

Although obesity is clearly identified as a risk factor for diabetes, the relationship between diabetes and metabolically healthy status of obesity is less clear. This study was aimed to evaluate the incidental risk of diabetes according to metabolically healthy status of obesity. 31,834 Korean men without diabetes categorized into six groups according to their metabolically healthy status stratified by degree of obesity were followed up for 5 years: metabolically healthy normal weight (MH-NW), metabolically healthy overweight (MH-OW), metabolically healthy obese (MHO), metabolically unhealthy normal weight (MU-NW), metabolically unhealthy overweight (MU-OW), and metabolically unhealthy obese (MUO). Cox proportional hazards analysis was used to measure the risk for diabetes according to their categories. While overall incidence was 9.0 %, incidence of diabetes was in proportion to the degree of obesity and metabolically healthy status (MH-NW: 6.3 %, MH-OW: 7.5 %, MHO: 9.2 %, MU-NW: 11.8 %, MU-OW: 14.9 %, MUO: 20.1 %). When MH-NW was set as reference, the adjusted HRs (95 % CI) for diabetes of the MH-OW, MHO, MU-NW, MU-OW, MUO compared to MH-NW were 1.18 (1.06-1.32), 1.58 (1.03-2.41), 1.81 (1.61-2.04), 2.36 (2.11-2.63), and 3.47 (2.84-4.24), respectively. In conclusion, risk for diabetes was in proportion to the degree of obesity in both metabolically healthy and unhealthy group. Metabolically healthy status was more significant determinant for incident diabetes than obesity itself.

A high-risk phenotype associates with reduced improvement in glycaemia during a lifestyle intervention in prediabetes

AIMS/HYPOTHESIS

Lack of reversal of prediabetes (impaired glucose tolerance and/or impaired fasting glucose) to normal glucose regulation (NGR) during a lifestyle intervention is strongly associated with a higher incidence of diabetes later in life. In the Tübingen Lifestyle Intervention Program (TULIP) we hypothesised that an at-risk phenotype may exist at baseline that associates with this nonresponse to the intervention.

METHODS

A total of 120 participants of TULIP with prediabetes at baseline were studied. Participants underwent 9 months of lifestyle intervention and had measurements of insulin secretion and insulin sensitivity during a 75 g OGTT, and measurements of liver fat content by proton magnetic resonance spectroscopy.

RESULTS

During the lifestyle intervention, 55% of the participants did not revert to NGR. Even among participants with the largest body fat loss (upper quartile: -6.9 ± 3.3%, mean ± SD), 40% did not revert to NGR. In this regard, we identified at baseline a high-risk phenotype (n = 72) consisting of low disposition index or low insulin sensitivity + nonalcoholic fatty liver disease (NAFLD) and a low-risk phenotype (n = 48, all other traits). While the adjusted decrease in body fat was almost identical between these phenotypes (-5.7 ± 15.3% vs -7.7 ± 15.2%, p = 0.49), the high-risk phenotype had a smaller decrease in adjusted 2 h blood glucose levels (-3.7 ± 20.3% vs -18.5 ± 20.0%, p = 0.0009). In addition, only 31% of the participants with the high-risk phenotype, but 67% with the low-risk phenotype, reverted to NGR (p < 0.0001). The odds ratio for reaching the status NGR was 4.54 (95% CI 2.08, 9.94) for participants having the low-risk phenotype.

CONCLUSIONS/INTERPRETATION

Stratification of individuals with prediabetes at baseline into a high-risk and a low-risk phenotype, based on corrected insulin secretion and insulin-resistant NAFLD, may help to determine the effectiveness of a lifestyle intervention to revert individuals to NGR.

Is the metabolically healthy obesity phenotype an irrelevant artifact for public health?

Some obese persons do not develop (at least in the short term) the metabolic complications of obesity that are thought to be causally linked to cardiovascular events or premature mortality. This phenomenon has been termed "metabolically healthy obesity" (MHO), and it has received much attention recently, to the extent that some authors argue that "new metrics" must be developed to estimate the risk associated with obesity beyond body mass index. In this commentary, we argue that the MHO phenotype is not benign and as such has very limited relevance as a public health target. More efforts must be allocated to reducing the distal and actual causal agents that lead to weight gain, instead of the current disproportionate scientific interest in the biological processes that explain the heterogeneity of obesity.

Metabolomics Reveals Metabolically Healthy and Unhealthy Obese Individuals Differ in their Response to a Caloric Challenge

OBJECTIVE

To determine if metabolically healthy obese (MHO) individuals have a different metabolic response to a standardized diet compared to lean healthy (LH) and metabolically unhealthy obese (MUO) individuals.

METHODS

Thirty adults (35-70 yrs) were classified as LH, MHO, and MUO according to anthropometric and clinical measurements. Participants consumed a standardized high calorie meal (~1330 kcal). Blood glucose and insulin were measured at fasting, and 15, 30, 60, 90 and 120 min postprandially. Additional blood samples were collected for the targeted analysis of amino acids (AAs) and derivatives, and fatty acids (FAs).

RESULTS

The postprandial response (i.e., area under the curve, AUC) for serum glucose and insulin were similar between MHO and LH individuals, and significantly lower than MUO individuals (p < 0.05). Minor differences were found in postprandial responses for AAs between MHO and MUO individuals, while three polyunsaturated FAs (linoleic acid, γ-linolenic acid, arachidonic acid) showed smaller changes in serum after the meal in MHO individuals compared to MUO. Fasting levels for various AAs (notably branched-chain AA) and FAs (e.g., saturated myristic and palmitic acids) were found to correlate with glucose and insulin AUC.

CONCLUSION

MHO individuals show preserved insulin sensitivity and a greater ability to adapt to a caloric challenge compared to MUO individuals.

Metabolically healthy obesity--does it exist?

The prevalence of obesity has been increasing worldwide over the past 30 years and is a major public health concern. Obesity is known to be associated with metabolic disturbances including insulin resistance and inflammation; however, there is a subset of obese subjects who have normal metabolic profiles, and they have been identified as the metabolically healthy obese (MHO). Several studies have described MHO as obese individuals who have high levels of insulin sensitivity and the absence of diabetes, dyslipidemia, or hypertension. The prevalence of MHO varies from 20 to 30% among obese individuals. This review will discuss the MHO phenotype; the differences between MHO and metabolically unhealthy obese (MUO) individuals; and the possible underlying mechanisms including adipocyte differentiation, immune regulation, and cellular energy metabolism.

Main characteristics of metabolically obese normal weight and metabolically healthy obese phenotypes

In this review, the influence of fat depots on insulin resistance and the main characteristics of metabolically obese normal-weight and metabolically healthy obese phenotypes are discussed. Medline/PubMed and Science Direct were searched for articles related to the terms metabolically healthy obesity, metabolically obese normal weight, adipose tissue, and insulin resistance. Normal weight and obesity might be heterogeneous in regard to their effects. Fat distribution and lower insulin sensitivity are the main factors defining phenotypes within the same body mass index. Although these terms are interesting, controversies about them remain. Future studies exploring these phenotypes will help elucidate the roles of adiposity and/or insulin resistance in the development of metabolic alterations.

[Pharmacological therapy versus bariatric surgery for patients with obesity and type 2 diabetes]

There is strong epidemiological evidence for an association between increased body weight and a higher incidence of type 2 diabetes. Moreover, reduction in body weight may delay the onset of type 2 diabetes. The basic therapy of type 2 diabetes includes lifestyle modifications, such as education, nutritional advice, increased physical activity, non-smoking and strategies to cope with stress. If lifestyle modifications are not successful, antidiabetic pharmacotherapy is stepwise intensified to achieve individual therapeutic targets; however, pharmacological treatment of type 2 diabetes frequently fails to prevent the progress of the disease and the manifestation of diabetes complications. Sustained weight reduction belongs to the individual treatment targets for patients with obesity and type 2 diabetes. Because conservative weight reduction strategies are frequently not successful, bariatric surgery has emerged as an effective treatment particularly for those patients with obesity-associated type 2 diabetes in whom a glycosylated hemoglobin (HbA1c) target < 7.5% could not be achieved with pharmacological therapy. Bariatric surgery should no longer be considered as the last option for patients with obesity-associated type 2 diabetes.

Consequences of obesity and weight loss: a devil's advocate position

Obesity is associated with multiple negative health consequences and current weight management guidelines recommend all obese persons to lose weight. However, recent evidence suggests that not all obese persons are negatively affected by their weight and that weight loss does not necessarily always improve health. The purpose of this review is not to trivialize the significant health risks associated with obesity, but to discuss subpopulations of obese people who are not adversely affected, or may even benefit from higher adiposity, and in who weight loss per se may not always be the most appropriate recommendation. More specifically, this review will take a devil's advocate position when discussing the consequences of obesity and weight loss for adults with established cardiovascular disease and type 2 diabetes, weight cyclers, metabolically healthy obese adults, youth, older adults and obese individuals who are highly fit.

Are metabolically healthy obese individuals really healthy?

Obesity has become one of the major public health concerns of the past decades, because it is a key risk factor for type 2 diabetes, cardiovascular diseases, dyslipidemia, hypertension, and certain types of cancer, which may lead to increased mortality. Both treatment of obesity and prevention of obesity-related diseases are frequently not successful. Moreover, a subgroup of individuals with obesity does not seem to be at an increased risk for metabolic complications of obesity. In this literature, this obesity subphenotype is therefore referred to as metabolically healthy obesity (MHO). Importantly, individuals with MHO do not significantly improve their cardio-metabolic risk upon weight loss interventions and may therefore not benefit to the same extent as obese patients with metabolic comorbidities from early lifestyle, bariatric surgery, or pharmacological interventions. However, it can be debated whether MHO individuals are really healthy, especially since there is no general agreement on accepted criteria to define MHO. In addition, overall health of MHO individuals may be significantly impaired by several psycho-social factors, psychosomatic comorbidities, low fitness level, osteoarthritis, chronic pain, diseases of the respiratory system, the skin, and others. There are still open questions about predictors, biological determinants, and the mechanisms underlying MHO and whether MHO represents a transient phenotype changing with aging and behavioral and environmental factors. In this review, the prevalence, potential biological mechanisms, and the clinical relevance of MHO are discussed.

Stability and changes in metabolically healthy overweight or obesity and risk of future diabetes: Niigata wellness study

OBJECTIVE

Stability and changes in obesity and metabolic health status from a baseline period and longitudinally investigated their impact on predicting future diabetes were assessed.

METHODS

Studied were 27,478 Japanese individuals without diabetes. Metabolically healthy (MH) was indicated by having ≤1 among impaired fasting glucose, hypertension, hypertriglyceridemia and low HDL cholesterol concentration. Metabolically abnormal (MA) was indicated by having ≥2 of those metabolic abnormalities. A cut-off value of BMI 25.0 defined overweight or obesity (O) or normal weight (NW). Hazard ratio (HR) for diabetes for a 6-year period was investigated after changes in phenotypes were assessed during the previous 2 years.

RESULTS

Compared with maintaining MH-NW, transitioning to MH-O from MH-NW resulted in a multivariate-adjusted HR of 1.96 (95% CI: 1.18, 3.25) for diabetes. With a stable MH-O the HR for diabetes was 2.59 (2.00, 3.34) while change from MH-O to MH-NW resulted in an HR of 1.30 (0.61, 2.76). Transitioning to MA-O from MH-O was associated with an HR of 7.09 (5.41, 9.30). With a stable MA-O the risk of diabetes was substantially elevated with an HR of 12.5 (10.5, 14.9).

CONCLUSIONS

Examining the transitory nature of apparently benign or unhealthy obese phenotypes was effective for differentiating high-risk individuals for future diabetes.

Downregulation of the acetyl-CoA metabolic network in adipose tissue of obese diabetic individuals and recovery after weight loss

AIMS/HYPOTHESIS

Not all obese individuals develop type 2 diabetes. Why some obese individuals retain normal glucose tolerance (NGT) is not well understood. We hypothesise that the biochemical mechanisms that underlie the function of adipose tissue can help explain the difference between obese individuals with NGT and those with type 2 diabetes.

METHODS

RNA sequencing was used to analyse the transcriptome of samples extracted from visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) of obese women with NGT or type 2 diabetes who were undergoing bariatric surgery. The gene expression data was analysed by bioinformatic visualisation and statistical analyses techniques.

RESULTS

A network-based approach to distinguish obese individuals with NGT from obese individuals with type 2 diabetes identified acetyl-CoA metabolic network downregulation as an important feature in the pathophysiology of type 2 diabetes in obese individuals. In general, genes within two reaction steps of acetyl-CoA were found to be downregulated in the VAT and SAT of individuals with type 2 diabetes. Upon weight loss and amelioration of metabolic abnormalities three months following bariatric surgery, the expression level of these genes recovered to levels seen in individuals with NGT. We report four novel genes associated with type 2 diabetes and recovery upon weight loss: ACAT1 (encoding acetyl-CoA acetyltransferase 1), ACACA (encoding acetyl-CoA carboxylase α), ALDH6A1 (encoding aldehyde dehydrogenase 6 family, member A1) and MTHFD1 (encoding methylenetetrahydrofolate dehydrogenase).

CONCLUSIONS/INTERPRETATION

Downregulation of the acetyl-CoA network in VAT and SAT is an important feature in the pathophysiology of type 2 diabetes in obese individuals. ACAT1, ACACA, ALDH6A1 and MTHFD1 represent novel biomarkers in adipose tissue associated with type 2 diabetes in obese individuals.

[Insulin or surgery? : the perspective of a diabetologist]

Obesity significantly increases the risk of developing type 2 diabetes by a factor of up to 9. Medical treatment of type 2 diabetes with lifestyle and pharmacological interventions frequently fails to prevent the progress of the disease and the manifestation of diabetes complications. In recent years bariatric metabolic surgery has emerged as an effective treatment for patients with obesity and type 2 diabetes. Compared to medical treatment alone, metabolic surgery has been shown to be more effective in reducing mortality, improving hyperglycemia, hypertension and dyslipidemia in randomized clinical trials among patients with obesity and type 2 diabetes. However, surgery also has the risk for acute perioperative complications, long-term micronutrient deficiencies and psychological problems. Weighing these risks against the benefits of significant weight loss and improved glycemic control, metabolic surgery seems to be a promising treatment option for obesity-associated type 2 diabetes. However, current guidelines and treatment algorithms for the treatment of type 2 diabetes either ignore or underestimate the potential of metabolic surgery. In my opinion, metabolic surgery should be considered earlier in the treatment of type 2 diabetes and obesity and no longer be considered as the last therapeutic option for patients with obesity-associated type 2 diabetes.

Metabolically healthy obesity from childhood to adulthood - Does weight status alone matter?

Up to 30% of obese people do not display the "typical" metabolic obesity-associated complications. For this group of patients, the term "metabolically healthy obese (MHO)" has been established during the past years and has been the focus of research activities. The development and severity of insulin resistance as well as (subclinical) inflammations seems to play a key role in distinguishing metabolically healthy from metabolically non-healthy individuals. However, an internationally consistent and accepted classification that might also include inflammatory markers as well as features of non-alcoholic fatty liver disease is missing to date, and available data - in terms of prevalence, definition and severity - are heterogeneous, both during childhood/adolescence and during adulthood. In addition, the impact of MHO on future morbidity and mortality compared to obese, metabolically non-healthy as well as normal weight, metabolically healthy individuals is absolutely not clear to date and even conflicting. This review summarizes salient literature related to that topic and provides insight into our current understanding of MHO, covering all age spans from childhood to adulthood.

Metabolically healthy and unhealthy obese--the 2013 Stock Conference report

Obesity is closely associated with cardiovascular diseases and type 2 diabetes, but some obese individuals, despite having excessive body fat, exhibit metabolic health that is comparable with that of lean individuals. The 'healthy obese' phenotype was described in the 1980s, but major advancements in its characterization were only made in the past five years. During this time, several new mechanisms that may be involved in health preservation in obesity were proposed through the use of transgenic animal models, use of sophisticated imaging techniques and in vivo measurements of insulin sensitivity. However, the main obstacle in advancing our understanding of the metabolically healthy obese phenotype and its related long-term health risks is the lack of a standardized definition. Here, we summarize the proceedings of the 13th Stock Conference of the International Association of the Study of Obesity. We describe the current research and highlight the unanswered questions and gaps in the field. Better understanding of metabolic health in obesity will assist in therapeutic decision-making and help identify therapeutic targets to improve metabolic health in obesity.

Metabolically healthy obesity, presence or absence of fatty liver, and risk of type 2 diabetes in Japanese individuals: Toranomon Hospital Health Management Center Study 20 (TOPICS 20)

OBJECTIVE

We investigated whether the metabolically healthy obese (MHO) phenotype was associated with an increased risk of the development of diabetes. If so, we aimed to determine what factors could explain this finding.

DESIGN, SETTING, AND PARTICIPANTS

Studied were 8090 Japanese individuals without diabetes. Metabolic health status was assessed by common clinical markers: blood pressure, triglycerides, high-density lipoprotein-cholesterol, and fasting glucose concentrations. The cutoff value for obesity or normal weight (NW) was a body mass index of 25.0 kg/m(2).

RESULTS

The 5-year incidence rate of diabetes was 1.2% (n = 58 of 4749) in metabolically healthy NW (MHNW) individuals, 2.8% (n = 20 of 719) in MHO individuals, 6.0% (n = 102 of 1709) in metabolically abnormal NW individuals, and 10.3% (n = 94 of 913) in metabolically abnormal obese individuals. Although MHO individuals had no or one metabolic factor, 47.8% had ultrasonographic fatty liver (FL). The MHO group had a significantly increased risk of diabetes compared with the MHNW group [multivariate adjusted odds ratio (OR) 2.23 (95% confidence interval [CI] 1.33, 3.75)], but this risk was attenuated after adjustment for FL. Compared with the MHNW/non-FL group, the risk of diabetes in the MHO/non-FL group was not significantly elevated [OR 1.01 (95% CI 0.35, 2.88)]. However, the MHO/FL and MHNW/FL groups had similarly elevated risks of diabetes [OR 4.09 (95% CI 2.20, 7.60) and 3.16 (1.78, 5.62), respectively].

CONCLUSIONS

Almost half of the MHO participants had FL, which partially explained the increased risk of diabetes among the obese phenotypes. The presence of FL should be evaluated to assess whether an individual was actually in a metabolically benign state for the prediction of diabetes.

Predicting the development of the metabolically healthy obese phenotype

Objective

The metabolically healthy (MHO) and unhealthy obese (MUHO) differ in terms of cardiovascular risk. However, little is known about predicting the development of these phenotypes and the future stability of the MHO phenotype. Therefore, we examined these two issues in the San Antonio Heart Study.

Design

Longitudinal, population-based study of cardiometabolic risk factors among Mexican Americans and non-Hispanic whites in San Antonio.

Subjects

The study sample included 2,368 participants with neither MUHO nor diabetes at baseline. Median follow-up was 7.8 years. MHO was defined as obesity with ≤1 metabolic abnormality; MUHO, as obesity with ≥2 abnormalities.

Results

At baseline, 1,595 and 498 individuals were non-obese with ≤1 and ≥2 metabolic abnormalities, respectively; 275 were MHO. Among non-obese individuals, independent predictors of incident MHO (OR for 1-SD change [95% CI]) included body mass index (8.12 [5.66 – 11.7]), triglycerides (0.52 [0.39 – 0.68]), and HDL-C (1.41 [1.11 – 1.81]), whereas independent predictors of incident MUHO included BMI (5.97 [4.58 – 7.77]) and triglycerides (1.26 [1.05 – 1.51]). Among participants with ≤1 metabolic abnormality, obesity was associated with greater odds of developing multiple metabolic abnormalities (OR 2.26 [1.74 – 2.95]).

Conclusions

Triglycerides and HDL-C may be useful for predicting progression to MHO. MHO may not be a stable condition, because it confers an increased risk of developing multiple metabolic abnormalities.

Metabolically healthy obesity and risk of incident type 2 diabetes: a meta-analysis of prospective cohort studies

The risk of type 2 diabetes among obese adults who are metabolically healthy has not been established. We systematically searched Medline (1946-August 2013) and Embase (1947-August 2013) for prospective studies of type 2 diabetes incidence (defined by blood glucose levels or self-report) among metabolically healthy obese adults (defined by body mass index [BMI] and normal cardiometabolic clustering, insulin profile or risk score) aged ≥18 years at baseline. We supplemented the analysis with an original effect estimate from the English Longitudinal Study of Ageing (ELSA), with metabolically healthy obesity defined as BMI ≥ 30 kg m(-2) and <2 of hypertension, impaired glycaemic control, systemic inflammation, adverse high-density lipoprotein cholesterol and adverse triglycerides. Estimates from seven published studies and ELSA were pooled using random effects meta-analyses (1,770 healthy obese participants; 98 type 2 diabetes cases). The pooled adjusted relative risk (RR) for incident type 2 diabetes was 4.03 (95% confidence interval = 2.66-6.09) in healthy obese adults and 8.93 (6.86-11.62) in unhealthy obese compared with healthy normal-weight adults. Although there was between-study heterogeneity in the size of effects (I(2)  = 49.8%; P = 0.03), RR for healthy obesity exceeded one in every study, indicating a consistently increased risk across study populations. Metabolically healthy obese adults show a substantially increased risk of developing type 2 diabetes compared with metabolically healthy normal-weight adults. Prospective evidence does not indicate that healthy obesity is a harmless condition.

Current issues in the identification and treatment of metabolically healthy but obese individuals

A unique subset of obese individuals who appear to be protected from the development of metabolic disturbances has been identified in the medical literature and is termed metabolically healthy but obese (MHO). Part of the issue is that there are no clear accepted criteria on the definition of MHO and the biological mechanisms to explain this phenotype are still unknown which render findings and/or conclusions difficult to interpret and making the application of this concept difficult in clinical practice. With the current definitions, the true prevalence of the MHO phenotype in the general population varies widely from approximately 3-57% of obese adults. In several prospective studies, the MHO individual has been associated with a similar risk of developing type 2 diabetes, cardiovascular disease and mortality when compared to healthy normal weight subjects; however, there is evidence to refute this concept. Furthermore, the current evidence cannot confirm that MHO subjects are permanently protected from the risk of developing metabolic disturbances associated with obesity. Currently, no standard practice guidelines for the treatment of MHO can be proposed, however, a regular surveillance of the waist circumference and cardio-metabolic risk factors such as elevated triglycerides, glycaemia, HOMA, C-reactive protein and low HDL, as well as the prevention of any further weight gain seem to represent the most prudent and sound attitude in the management of MHO subjects.

Relationships of body composition and liver fat content with insulin resistance in obesity-matched adolescents and adults

OBJECTIVE

While in adults not total body- or visceral fat mass, but liver fat content was found to independently determine insulin resistance, it is unclear whether these relationships are already present in obese adolescents.

METHODS

Thirty-nine overweight/obese adolescents were matched for sex and BMI with 39 adults. To compare the age- and sex-specific BMI values of adolescents and adults, the percentile value of each adolescent was projected to the age of 18. Body fat depots were quantified by whole-body magnetic resonance (MR) imaging. Liver fat content was measured with (1)H-MR spectroscopy. Insulin resistance was estimated from the homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Compared to overweight and obese adults, adolescents had higher HOMA-IR (P < 0.001) and lower lean body mass (P = 0.002). Furthermore, they had higher total body- (P = 0.02), but lower visceral- (P < 0.001) fat mass, while liver fat content was not significantly different between the groups (P = 0.16). In both groups liver fat content (both P ≤ 0.007), but not total body- or visceral fat mass (all P ≥ 0.64) was an independent predictor of insulin resistance.

CONCLUSIONS

Having lower visceral fat mass, overweight and obese adolescents are more insulin resistant than sex- and BMI-matched adults. Liver fat content, but not total body- or visceral fat mass, is an independent determinant of insulin resistance in adolescents.

The prevalence of metabolic syndrome and metabolically healthy obesity in Europe: a collaborative analysis of ten large cohort studies

BACKGROUND

Not all obese subjects have an adverse metabolic profile predisposing them to developing type 2 diabetes or cardiovascular disease. The BioSHaRE-EU Healthy Obese Project aims to gain insights into the consequences of (healthy) obesity using data on risk factors and phenotypes across several large-scale cohort studies. Aim of this study was to describe the prevalence of obesity, metabolic syndrome (MetS) and metabolically healthy obesity (MHO) in ten participating studies.

METHODS

Ten different cohorts in seven countries were combined, using data transformed into a harmonized format. All participants were of European origin, with age 18-80 years. They had participated in a clinical examination for anthropometric and blood pressure measurements. Blood samples had been drawn for analysis of lipids and glucose. Presence of MetS was assessed in those with obesity (BMI ≥ 30 kg/m2) based on the 2001 NCEP ATP III criteria, as well as an adapted set of less strict criteria. MHO was defined as obesity, having none of the MetS components, and no previous diagnosis of cardiovascular disease.

RESULTS

Data for 163,517 individuals were available; 17% were obese (11,465 men and 16,612 women). The prevalence of obesity varied from 11.6% in the Italian CHRIS cohort to 26.3% in the German KORA cohort. The age-standardized percentage of obese subjects with MetS ranged in women from 24% in CHRIS to 65% in the Finnish Health2000 cohort, and in men from 43% in CHRIS to 78% in the Finnish DILGOM cohort, with elevated blood pressure the most frequently occurring factor contributing to the prevalence of the metabolic syndrome. The age-standardized prevalence of MHO varied in women from 7% in Health2000 to 28% in NCDS, and in men from 2% in DILGOM to 19% in CHRIS. MHO was more prevalent in women than in men, and decreased with age in both sexes.

CONCLUSIONS

Through a rigorous harmonization process, the BioSHaRE-EU consortium was able to compare key characteristics defining the metabolically healthy obese phenotype across ten cohort studies. There is considerable variability in the prevalence of healthy obesity across the different European populations studied, even when unified criteria were used to classify this phenotype.

Risk of developing diabetes and cardiovascular disease in metabolically unhealthy normal-weight and metabolically healthy obese individuals

CONTEXT

The risk of cardiovascular disease (CVD) and type 2 diabetes mellitus (DM) associated with obesity appears to be influenced by the coexistence of other metabolic abnormalities.

OBJECTIVE

We examined the risk of developing CVD and DM in metabolically healthy obese (MHO) and metabolically unhealthy normal weight (MUH-NW) individuals.

DESIGN AND SETTING

We analyzed prospective data of the San Antonio Heart Study, a population-based study among Mexican Americans and non-Hispanic whites (median follow-up, 7.4 y).

PARTICIPANTS

Incident DM and CVD were assessed in 2814 and 3700 participants aged 25 to 64 years, respectively.

MAIN MEASURES

MHO was defined as obesity (body mass index ≥ 30 kg/m(2)) with no more than one metabolic abnormality, and MUH-NW was defined as body mass index <25 kg/m(2) with two or more abnormalities.

RESULTS

In logistic regression models, BMI was associated with incident DM after controlling for demographics, family history of DM, and fasting glucose (odds ratio × 1 SD, 1.7 [95% CI, 1.5-2.0]). Both MUH-NW and MHO individuals had an increased DM risk (2.5 [1.1-5.6] and 3.9 [2.0-7.4], respectively). Similarly, BMI was related to incident CVD after adjusting for demographics and Framingham risk score (1.3 [1.1-1.6]). Incident CVD was also increased in MUH-NW and MHO individuals (2.9 [1.3-6.4] and 3.9 [1.9-7.8], respectively). Results were consistent across gender and ethnic categories.

CONCLUSION

The risk of developing DM and CVD is increased in MUH-NW and MHO individuals. Screening for obesity and other metabolic abnormalities should be routinely performed in clinical practice to institute appropriate preventive measures.

Introduction to personalized medicine in diabetes mellitus

The world is facing an epidemic rise in diabetes mellitus (DM) incidence, which is challenging health funders, health systems, clinicians, and patients to understand and respond to a flood of research and knowledge. Evidence-based guidelines provide uniform management recommendations for "average" patients that rarely take into account individual variation in susceptibility to DM, to its complications, and responses to pharmacological and lifestyle interventions. Personalized medicine combines bioinformatics with genomic, proteomic, metabolomic, pharmacogenomic ("omics") and other new technologies to explore pathophysiology and to characterize more precisely an individual's risk for disease, as well as response to interventions. In this review we will introduce readers to personalized medicine as applied to DM, in particular the use of clinical, genetic, metabolic, and other markers of risk for DM and its chronic microvascular and macrovascular complications, as well as insights into variations in response to and tolerance of commonly used medications, dietary changes, and exercise. These advances in "omic" information and techniques also provide clues to potential pathophysiological mechanisms underlying DM and its complications.

A metabolically healthy obese phenotype in hispanic participants in the IRAS family study

OBJECTIVE

Some obese individuals appear to be protected from developing type 2 diabetes mellitus and cardiovascular disease (CVD). This has led to characterizing body size phenotypes based on cardiometabolic risk factors specifically as obese or overweight, and as metabolically healthy (MH) or metabolically abnormal (MA) based upon blood pressure, lipids, glucose homeostasis, and inflammatory parameters. The aim of this study was to measure the prevalence of and describe fat distribution across these phenotypes in a minority population.

DESIGN AND METHODS

Hispanic participants (N = 1054) in the IRAS Family Study were categorized into different body size phenotypes. Computed tomography (CT) abdominal scans were evaluated for measures of nonalcoholic fatty liver disease (NAFLD) and abdominal fat distribution. Statistical models adjusting for familial relationships were estimated.

RESULTS

Seventy percent (70%) of the Hispanic cohort was overweight (32%) or obese (38%). Forty-one percent (n = 138) of overweight participants and 19% (n = 74) of obese participants met criteria for MH. Adjusted analyses showed the MH phenotype was associated with lower visceral adipose tissue (VAT) and higher liver density (indicating lower fat content) in obese participants (p = 0.0005 and p = 0.0002, respectively), and lower VAT but not liver density in overweight participants (p = 0.008 and p = 0.162, respectively) compared to their MA counterparts. Odds of NAFLD were reduced in MH obese (OR = 0.34, p = 0.0007) compared to MA obese. VAT did not differ between MH obese or overweight and normal weight groups.

CONCLUSIONS

These findings suggest that lower levels of visceral and liver fat, despite overall increased total body fat, may be a defining feature of MH obesity in Hispanic Americans.

Defining metabolically healthy obesity: role of dietary and lifestyle factors

Background

There is a current lack of consensus on defining metabolically healthy obesity (MHO). Limited data on dietary and lifestyle factors and MHO exist. The aim of this study is to compare the prevalence, dietary factors and lifestyle behaviours of metabolically healthy and unhealthy obese and non-obese subjects according to different metabolic health criteria.

Method

Cross-sectional sample of 1,008 men and 1,039 women aged 45-74 years participated in the study. Participants were classified as obese (BMI ≥30kg/m²) and non-obese (BMI <30kg/m²). Metabolic health status was defined using five existing MH definitions based on a range of cardiometabolic abnormalities. Dietary composition and quality, food pyramid servings, physical activity, alcohol and smoking behaviours were examined.

Results

The prevalence of MHO varied considerably between definitions (2.2% to 11.9%), was higher among females and generally increased with age. Agreement between MHO classifications was poor. Among the obese, prevalence of MH was 6.8% to 36.6%. Among the non-obese, prevalence of metabolically unhealthy subjects was 21.8% to 87%. Calorie intake, dietary macronutrient composition, physical activity, alcohol and smoking behaviours were similar between the metabolically healthy and unhealthy regardless of BMI. Greater compliance with food pyramid recommendations and higher dietary quality were positively associated with metabolic health in obese (OR 1.45-1.53 unadjusted model) and non-obese subjects (OR 1.37-1.39 unadjusted model), respectively. Physical activity was associated with MHO defined by insulin resistance (OR 1.87, 95% CI 1.19-2.92, p = 0.006).

Conclusion

A standard MHO definition is required. Moderate and high levels of physical activity and compliance with food pyramid recommendations increase the likelihood of MHO. Stratification of obese individuals based on their metabolic health phenotype may be important in ascertaining the appropriate therapeutic or intervention strategy.

Metabolically healthy obesity: epidemiology, mechanisms, and clinical implications

Obesity has become a worldwide epidemic that poses substantial health problems for both individuals and society. However, a proportion of obese individuals might not be at an increased risk for metabolic complications of obesity and, therefore, their phenotype can be referred to as metabolically healthy obesity. This novel concept of metabolically healthy obesity might become increasingly important to stratify individuals in the clinical treatment of obesity. However, no universally accepted criteria exist to define metabolically healthy obesity. Furthermore, many questions have been raised regarding the biological basis of this phenotype, the transitory nature of metabolically healthy obesity over time, and predictors of this phenotype. We describe the observational studies that gave rise to the idea of metabolically healthy obesity and the key parameters that can help to distinguish it from the general form of obesity. We also discuss potential biological mechanisms underlying metabolically healthy obesity and its public health and clinical implications.

Pleiotropic effects of obesity-susceptibility loci on metabolic traits: a meta-analysis of up to 37,874 individuals

AIMS/HYPOTHESIS

Genetic pleiotropy may contribute to the clustering of obesity and metabolic conditions. We assessed whether genetic variants that are robustly associated with BMI and waist-to-hip ratio (WHR) also influence metabolic and cardiovascular traits, independently of obesity-related traits, in meta-analyses of up to 37,874 individuals from six European population-based studies.

METHODS

We examined associations of 32 BMI and 14 WHR loci, individually and combined in two genetic predisposition scores (GPSs), with glycaemic traits, blood lipids and BP, with and without adjusting for BMI and/or WHR.

RESULTS

We observed significant associations of BMI-increasing alleles at five BMI loci with lower levels of 2 h glucose (RBJ [also known as DNAJC27], QPTCL: effect sizes -0.068 and -0.107 SD, respectively), HDL-cholesterol (SLC39A8: -0.065 SD, MTCH2: -0.039 SD), and diastolic BP (SLC39A8: -0.069 SD), and higher and lower levels of LDL- and total cholesterol (QPTCL: 0.041 and 0.042 SDs, respectively, FLJ35779 [also known as POC5]: -0.042 and -0.041 SDs, respectively) (all p < 2.4 × 10(-4)), independent of BMI. The WHR-increasing alleles at two WHR loci were significantly associated with higher proinsulin (GRB14: 0.069 SD) and lower fasting glucose levels (CPEB4: -0.049 SD), independent of BMI and WHR. A higher GPS-BMI was associated with lower systolic BP (-0.005 SD), diastolic BP (-0.006 SD) and 2 h glucose (-0.013 SD), while a higher GPS-WHR was associated with lower HDL-cholesterol (-0.015 SD) and higher triacylglycerol levels (0.014 SD) (all p < 2.9 × 10(-3)), independent of BMI and/or WHR.

CONCLUSIONS/INTERPRETATION

These pleiotropic effects of obesity-susceptibility loci provide novel insights into mechanisms that link obesity with metabolic abnormalities.

Metabolically healthy obesity: definitions, determinants and clinical implications

Obesity is associated with increased risk of developing metabolic syndrome (MetS), type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) leading to higher all-cause mortality. However accumulating evidence suggests that not all obese subjects are at increased cardiometabolic risk and that the "metabolically healthy obese" (MHO) phenotype may exist in the absence of metabolic abnormalities. Despite the knowledge of the existence of obese metabolic phenotypes for some time now there is no standard set of criteria to define metabolic health, thus impacting on the accurate estimation of the prevalence of the MHO phenotype and making comparability between studies difficult. Furthermore prospective studies tracking the development of cardiometabolic disease and mortality in MHO have also produced conflicting results. Limited data regards the determinants of the MHO phenotype exist, particularly in relation to dietary and lifestyle behaviours. In light of the current obesity epidemic it is clear that current "one size fits all" approaches to tackle obesity are largely unsuccessful. Whether dietary, lifestyle and/or therapeutic interventions based on stratification of obese individuals according to their metabolic health phenotype are more effective remains to be seen, with limited and conflicting data available so far. This review will present the current state of the art including the epidemiology of MHO and its definitions, what factors may be important in determining metabolic health status and finally, some potential implications of the MHO phenotype in the context of obesity diagnosis, interventions and treatment.

Ectopic fat: the true culprit linking obesity and cardiovascular disease?

Obesity is a major risk factor for cardiovascular disease and its complications. However, not all fat depots share the same characteristics. Recent studies have found that ectopic rather than subcutaneous fat accumulation is associated with increased cardiometabolic risk. However, ectopic fat accumulation can be seen initially as a protective mechanism against lipotoxicity. Subsequently the adipose tissue becomes dysfunctional, thus inducing systemic metabolic alterations (through release of cytokines) or specific organ dysfunctions. The purpose of this review is to summarise the current available data on the impact of excess adiposity vs ectopic fat in the development of cardio-metabolic diseases.

The cancer-associated FGFR4-G388R polymorphism enhances pancreatic insulin secretion and modifies the risk of diabetes

The fibroblast growth factor receptor 4 (FGFR4)-R388 single-nucleotide polymorphism has been associated with cancer risk and prognosis. Here we show that the FGFR4-R388 allele yields a receptor variant that preferentially promotes STAT3/5 signaling. This STAT activation transcriptionally induces Grb14 in pancreatic endocrine cells to promote insulin secretion. Knockin mice with the FGFR4 variant allele develop pancreatic islets that secrete more insulin, a feature that is reversed through Grb14 deletion and enhanced with FGF19 administration. We also show in humans that the FGFR4-R388 allele enhances islet function and may protect against type 2 diabetes. These data support a common genetic link underlying cancer and hyperinsulinemia.

A weight loss diet intervention has a similar beneficial effect on both metabolically abnormal obese and metabolically healthy but obese premenopausal women

BACKGROUND/AIMS

We studied the effect of a 12-week energy-restricted diet intervention on cardiometabolic risk in two groups of nonmorbid obese premenopausal Caucasian women, i.e. a metabolically abnormal obese (MAO) and a metabolically healthy but obese (MHO) group.

METHODS

The participants were 53 MAO and 25 MHO women (age range 19-49 years; body mass index inclusion criterion: 30-39.9). We assessed changes in body weight and composition, blood lipids, insulin resistance, hepatic enzymes, inflammatory markers and adipocytokines.

RESULTS

Overall, many of the study outcomes improved with the intervention in both MAO and MHO participants, but there was no difference in the magnitude of change between the groups. Body weight, waist circumference and total fat mass decreased significantly in response to the intervention in both MAO and MHO women (all p < 0.001). Fasting insulin, insulin resistance (homeostasis model assessment), hepatic enzymes (alanine aminotransferase and γ-glutamyltransferase), fatty liver index and leptin levels also decreased in both groups after the intervention (all p < 0.001), whereas total cholesterol, triglycerides and C-reactive protein decreased significantly only in MAO women (all p < 0.001).

CONCLUSION

These findings reinforce the idea that MHO women would also benefit from a lifestyle weight reduction intervention.

Fraction of unsaturated fatty acids in visceral adipose tissue (VAT) is lower in subjects with high total VAT volume - a combined 1 H MRS and volumetric MRI study in male subjects

Visceral adipose tissue (VAT) is thought to play an important role in the pathogenesis of obesity and insulin resistance. However, little is known about the composition of VAT with regard to the amount of mono- (MUFAs) and polyunsaturated fatty acids (PUFAs) in triglycerides. Volume-selective MRS was performed in addition to MRI for the quantification of VAT. Analysis comprised proton signals from the vinyl-H group (H-C=C-H), including protons from MUFA+PUFA, and diallylic-H, i.e. methylene-interrupted PUFAs. The methyl (-CH(3) ) resonance, which is the only peak with a defined number of protons/triglyceride (n=9), served as reference. Twenty male subjects participated in this prospective study and underwent MRS of VAT on a 3-T whole-body unit. Spectra were recorded by a single-voxel stimulated echo acquisition mode (STEAM) technique (TE/TM/TR=20/10/4000 ms; volume of interest between 20 × 25 × 20 and 30 × 30 × 20 mm(3); 48-80 acquisitions depending on the size of the volume of interest; bandwidth, 1200 Hz). Post-processing was performed by a Java-based magnetic resonance user interface (jMRUI; AMARES). The volume of VAT was quantified in a separate session on a 1.5-T imager a few days prior to the MRS session by T(1) -weighted imaging. The relative amount of VAT was calculated as a percentage of body weight (%VAT). Ratios of vinyl-H to -CH(3) and diallylic-H to -CH(3) were calculated. All spectra recorded from VAT were of high quality, enabling reliable quantification of the mentioned resonances. %VAT and vinyl-H/CH(3) varied over a broad range (2.8-8.3% and 0.45-0.64, respectively). A strong negative correlation between %VAT and vinyl-H/CH(3) was found (r= -0.92), whereas diallylic-H/CH(3) alone was clearly less well correlated with %VAT (r= -0.21). The composition of VAT shows strong interindividual variations. The greater the total amount of VAT, the less unsaturated the fatty acids. This is a preliminary result in mainly obese male subjects, and it remains to be determined whether this correlation holds for other cohorts of different age, gender and body mass index. Furthermore, changes in VAT composition during weight loss or different forms of diet have yet to be examined.

Visceral fat and metabolic inflammation: the portal theory revisited

Abdominal (central) obesity strongly correlates with (hepatic) insulin resistance and type 2 diabetes. Among several hypotheses that have been formulated, the 'portal theory' proposes that the liver is directly exposed to increasing amounts of free fatty acids and pro-inflammatory factors released from visceral fat into the portal vein of obese patients, promoting the development of hepatic insulin resistance and liver steatosis. Thus, visceral obesity may be particularly hazardous in the pathogenesis of insulin resistance and type 2 diabetes. Herein, we will critically review existing evidence for a potential contribution of portally drained free fatty acids and/or cytokines to the development of hepatic insulin resistance.

Are there still healthy obese patients?

PURPOSE OF REVIEW

Obesity is associated with an increased risk of premature death and represents a fast growing worldwide health problem that is reaching epidemic proportions. Obesity significantly increases the risk of developing metabolic disorders, hypertension, coronary heart disease, stroke, and several types of cancer. However, a subgroup of 'healthy' obese patients seems to be protected against metabolic and cardiovascular obesity comorbidities. This review focuses on potential mechanisms underlying the healthy obese subphenotype.

RECENT FINDINGS

Individuals with obesity typically develop type 2 diabetes, dyslipidemia, fatty liver disease, gout, hypertension, and cardiovascular disease. In the past years it became clear that up to 30% of obese patients are metabolically healthy with insulin sensitivity similar to healthy lean individuals, lower liver fat content, and lower intima media thickness of the carotid artery than the majority of metabolically 'unhealthy' obese patients. Recent studies suggest that protection against development of hepatic steatosis, ectopic fat deposition, inflammation of visceral adipose tissue, and adipose tissue dysfunction contributes to healthy obesity.

SUMMARY

For the stratification of obesity treatment, definition of metabolically healthy or high-risk phenotypes will facilitate the identification of the obese person who will benefit the most from early lifestyle, bariatric surgery, or pharmacological interventions.

Potential mechanisms for the emerging link between obesity and increased intestinal permeability

Recently, increased attention has been paid to the link between gut microbial composition and obesity. Gut microbiota is a source of endotoxins whose increase in plasma is related to obesity and insulin resistance through increased intestinal permeability in animal models; however, this relationship still needs to be confirmed in humans. That intestinal permeability is subject to change and that it might be the interface between gut microbiota and endotoxins in the core of metabolic dysfunctions reinforce the need to understand the mechanisms involved in these aspects to direct more efficient therapeutic approaches. Therefore, in this review, we focus on the emerging link between obesity and increased intestinal permeability, including the possible factors that contribute to increased intestinal permeability in obese subjects. We address the concept of intestinal permeability, how it is measured, and the intestinal segments that may be affected. We then describe 3 factors that may have an influence on intestinal permeability in obesity: microbial dysbiosis, dietary pattern (high-fructose and high-fat diet), and nutritional deficiencies. Gaps in the current knowledge of the role of Toll-like receptors ligands to induce insulin resistance, the routes for lipopolysaccharide circulation, and the impact of altered intestinal microbiota in obesity, as well as the limitations of current permeability tests and other potential useful markers, are discussed. More studies are needed to reveal how changes occur in the microbiota. The factors such as changes in the dietary pattern and the improvement of nutritional deficiencies appear to influence intestinal permeability, and impact metabolism must be examined. Also, additional studies are necessary to better understand how probiotic supplements, prebiotics, and micronutrients can improve stress-induced gastrointestinal barrier dysfunction and the influence these factors have on host defense. Hence, the topics presented in this review may be beneficial in directing future studies that assess gut barrier function in obesity.

Randomized trial of exercise effect on intrahepatic triglyceride content and lipid kinetics in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) and alterations in hepatic lipoprotein kinetics are common metabolic complications associated with obesity. Lifestyle modification involving diet-induced weight loss and regular exercise decreases intrahepatic triglyceride (IHTG) content and very low density lipoprotein (VLDL) triglyceride (TG) secretion rate. The aim of this study was to evaluate the weight loss-independent effect of following the physical activity guidelines recommended by the Department of Health and Human Services on IHTG content and VLDL kinetics in obese persons with NAFLD. Eighteen obese people (body mass index [BMI]: 38.1 ± 4.6 kg/m(2)) with NAFLD were randomized to 16 weeks of exercise training (45%-55% VO(2peak) , 30-60 minutes × 5 days/week; n = 12) or observation (control; n = 6). Magnetic resonance spectroscopy and stable isotope tracer infusions in conjunction with compartmental modeling were used to evaluate IHTG content and hepatic VLDL-TG and apolipoprotein B-100 (apoB-100) secretion rates. Exercise training resulted in a 10.3% ± 4.6% decrease in IHTG content (P < 0.05), but did not change total body weight (103.1 ± 4.2 kg before and 102.9 ± 4.2 kg after training) or percent body fat (38.9% ± 2.1% before and 39.2% ± 2.1% after training). Exercise training did not change the hepatic VLDL-TG secretion rate (17.7 ± 3.9 μmol/min before and 16.8 ± 5.4 μmol/min after training) or VLDL-apoB-100 secretion rate (1.5 ± 0.5 nmol/min before and 1.6 ± 0.6 nmol/min after training).

CONCLUSION

Following the Department of Health and Human Services recommended physical activity guidelines has small but beneficial effects on IHTG content, but does not improve hepatic lipoprotein kinetics in obese persons with NAFLD.

Insulin-sensitive obesity in humans - a 'favorable fat' phenotype?

In most humans, obesity and insulin resistance coexist. However, a unique group of obese individuals, who exhibit better insulin sensitivity than expected for their adiposity, has been the focus of recent research interest. We critically examine cross-sectional and lifestyle intervention studies in obese humans classified as 'insulin-sensitive' versus 'insulin-resistant' and review the few longitudinal studies comparing rates of cardiovascular disease, type 2 diabetes and all-cause mortality in these groups of individuals. We suggest that reduced deposition of fat, particularly of bioactive lipid intermediates, in muscle and liver is potentially protective. We propose that dynamic interventional studies in insulin-sensitive obese humans may increase understanding of the metabolic factors that play a role in obesity-associated insulin resistance in humans.

Insulin sensitivity deteriorates after short-term lifestyle intervention in the insulin sensitive phenotype of obesity

OBJECTIVE

To investigate the effects of a 3-month lifestyle intervention on insulin sensitivity and its related cardiometabolic factors in obese patients.

METHODS

Anthropometry, body composition, oral glucose tolerance test, lipids, alanine aminotransferase, insulin sensitivity (insulinogenic index (ISI), homeostasis model assessment, β-cell performance (disposition index)) were evaluated in 263 obese women and 93 obese men before and after 3 months of hypocaloric low fat/high protein diet associated with physical activity 30 min/day.

RESULTS

Patients were divided into 3 groups according to the intervention-induced ISI changes: group 1 (decrease), group 2 (stability) and group 3 (increase). Insulin sensitivity and the disposition index were significantly higher before the intervention in group 1 than in group 3. BMI, waist circumference, and fat mass significantly decreased in groups 1 and 3 in both sexes. β-cell performance decreased in group 1 and increased in group 3. Metabolic variables improved in group 3, whereas glucose levels increased in women of group 1. The post-intervention insulin sensitivity was lower in group 1 than in group 3.

CONCLUSION

Lifestyle intervention induces changes in insulin sensitivity and metabolic factors that depend on the pre-intervention degree of insulin sensitivity. Weight loss leads to metabolic benefits in insulin-resistant, obese patients, whereas it may paradoxically worsen the metabolic conditions in the insulin-sensitive phenotype of obesity.

All-cause mortality risk of metabolically healthy obese individuals in NHANES III

Mortality risk across metabolic health-by-BMI categories in NHANES-III was examined. Metabolic health was defined as: (1) homeostasis model assessment-insulin resistance (HOMA-IR) <2.5; (2) ≤2 Adult Treatment Panel (ATP) III metabolic syndrome criteria; (3) combined definition using ≤1 of the following: HOMA-IR ≥1.95 (or diabetes medications), triglycerides ≥1.7 mmol/L, HDL-C <1.04 mmol/L (males) or <1.30 mmol/L (females), LDL-C ≥2.6 mmol/L, and total cholesterol ≥5.2 mmol/L (or cholesterol-lowering medications). Hazard ratios (HR) for all-cause mortality were estimated with Cox regression models. Nonpregnant women and men were included (n = 4373, mean ± SD, age 37.1 ± 10.9 years, BMI 27.3 ± 5.8 kg/m², 49.4% female). Only 40 of 1160 obese individuals were identified as MHO by all definitions. MHO groups had superior levels of clinical risk factors compared to unhealthy individuals but inferior levels compared to healthy lean groups. There was increased risk of all-cause mortality in metabolically unhealthy obese participants regardless of definition (HOMA-IR HR 2.07 (CI 1.3-3.4), P < 0.01; ATP-III HR 1.98 (CI 1.4-2.9), P < 0.001; combined definition HR 2.19 (CI 1.3-3.8), P < 0.01). MHO participants were not significantly different from healthy lean individuals by any definition. While MHO individuals are not at significantly increased risk of all-cause mortality, their clinical risk profile is worse than that of metabolically healthy lean individuals.