Addressing Reverse Causation Bias in the Obesity Paradox Is Not "One Size Fits All"

Metabolomic Profiling in Ischemic Stroke: Unraveling the Influence of Obesity and Identifying Potential Biomarkers Using 1H NMR Spectroscopy

Ischemic stroke (IS) is emerging as an increasingly serious social issue with elusive etiology, few diagnostic markers, and limited treatment methods. Another concern in contemporary society is the prevalence of obesity, which is indicative of suboptimal well-being. Despite its association with established risk factors for stroke (such as hypertension and diabetes), several studies have reported a controversial phenomenon known as the "obesity paradox," whereby certain obese patients with stroke exhibited unexpectedly positive outcomes. In this study, a total of 68 plasma samples were collected including 36 controls and 32 IS patients, with further differentiation between obese and non-obese individuals in each group. A quantitative metabonomic approach based on 1H nuclear magnetic resonance (1H NMR) was employed to identify differential metabolic markers of IS, and elucidate the impact of obesity on IS. The final results demonstrated that obesity did not have a significant impact on metabolites. It is important to note, however, that reliance on BMI as the sole indicator of obesity may be insufficient. Additional parameters, such as waist-to-hip ratio and waist circumference, should be considered. Furthermore, the impact of obesity on stroke is probably mediated through metabolic health, making it an intermediate factor rather than a direct cause. Additionally, the study identified approximately 30 metabolites exhibiting significant alterations in IS patients, with the primary metabolic pathways being energy metabolism, amino acid metabolism, lipid metabolism, and folic acid deficiency. These findings are significant for comprehending the potential mechanisms of IS and facilitating its rapid and early diagnosis for effective treatment.

Role of obesity in pathogenesis of acute pancreatitis

Acute pancreatitis (AP) is one of the most common digestive disorders that cause hospitalization. While most of patients with AP have a mild to moderate disease and recover rapidly, about 20% of patients with AP have a severe disease and experience substantial morbidity and mortality from local and/or systemic compli-cations. The incidence of obesity has increased worldwide, and its epidemiological characteristics and rising trend are consistent with those of AP. Therefore, obesity has probably contributed to the increase in the incidence and severity of AP. However, previous studies have generated conflicting results, and some studies demonstrated that obesity is a protective factor in patients with AP. Here we discuss the role of obesity in the pathogenesis of AP and the underlying mechanisms based on clinically relevant studies.

Obesity, metabolic health and clinical outcomes after incident cardiovascular disease: A nationwide population-based cohort study

BACKGROUND

The association between metabolic syndrome and increased cardiovascular disease (CVD) risk is well-established. However, in patients with incident CVD, the relationship between obesity, metabolic health, and subsequent CVD and mortality outcomes are less well-established. This study investigated the association between body mass index (BMI), metabolic health and the risk of subsequent cardiovascular mortality and morbidity outcomes in patients with incident CVD events.

METHODS

This cohort study identified 130 685 patients from the nationwide Clinical Practice Research Datalink (CPRD GOLD) and Hospital Episode Statistics (HES) databases in the United Kingdom. Patients were ≥18 years with incident CVD [coronary heart disease (CHD), stroke, or peripheral vascular disease (PVD)] between 1 January 1998 and 31 December 2017. BMI (in kg/m2 ) was categorized as underweight (<18.5), normal (18.5-24.9), overweight (25.0-29.9) and obese (≥30). Within each BMI category, patients were grouped by increasing count of 1, 2 or 3 metabolic risk factors [RF] (dyslipidaemia, diabetes mellitus and hypertension) and were regarded as metabolically unhealthy while absence of these factors was considered metabolically healthy (MH). Multivariable Cox regression was used to assess the risk (hazard ratio with 95% confidence interval) of subsequent outcomes (non-fatal CHD, stroke, PVD, incident heart failure, CVD-mortality and all-cause mortality) in BMI subgroups with incremental count of metabolic RFs.

RESULTS

During a median follow-up of 13.0 years, a higher BMI was associated with reduced risk for stroke, PVD, CVD-mortality and all-cause mortality within each metabolic risk category, while increasing metabolic RFs within each BMI subgroup accounted for increasing risks. When compared with patients with normal BMI and no RF, CVD-mortality risk in overweight patients with no RF was 0.76 (0.70-0.84), and in obese patients with no RF was 0.85 (0.76-0.96). The respective risk for all-cause mortality in patients with overweight and no RF was 0.69 (0.65-0.72), and in obese patients with no RF was 0.75 (0.70-0.79). Subsequent outcomes of stroke and PVD showed similar trends. In contrast, the risk of subsequent non-fatal CHD events and incident HF increased with higher BMI and with incremental metabolic risk factors within each BMI category. Underweight was constantly associated with increased risk for all outcomes regardless of the presence of metabolic RFs except for non-fatal CHD events.

CONCLUSIONS

In patients with incident CVD, overweight and obesity were related to a more favourable prognosis for subsequent stroke, PVD and mortality (CVD-related and all-cause) irrespective of the presence of other metabolic risk factors.

Obesity Paradox: Fact or Fiction?

PURPOSE OF REVIEW

Obesity is related to several comorbidities such as type 2 diabetes mellitus, cardiovascular disease, heart failure, and various types of cancers. While the detrimental effect of obesity in both mortality and morbidity has been well established, the concept of the obesity paradox in specific chronic diseases remains a topic of continuous interest. In the present review, we examine the controversial issues around the obesity paradox in certain conditions such as cardiovascular disease, several types of cancer and chronic obstructive pulmonary disease, and the factors that may confound the relation between obesity and mortality.

RECENT FINDINGS

We refer to the obesity paradox when particular chronic diseases exhibit an interesting "paradoxical" protective association between the body mass index (BMI) and clinical outcomes. This association, however, may be driven by multiple factors among which the limitations of the BMI itself; the unintended weight loss precipitated by chronic illness; the various phenotypes of obesity, i.e., sarcopenic obesity or the athlete's obesity phenotype; and the cardiorespiratory fitness levels of the included patients. Recent evidence highlighted that previous cardioprotective medications, obesity duration, and smoking status seem to play a role in the obesity paradox. The obesity paradox has been described in a plethora of chronic diseases. It cannot be emphasized enough that the incomplete information received from a single BMI measurement may interfere with outcomes of studies arguing in favor of the obesity paradox. Thus, the development of carefully designed studies, unhampered by confounding factors, is of great importance.

Diagnosis, Prevalence and Significance of Obesity in a Cohort of CKD Patients

BACKGROUND

data regarding the association between obesity and morbidity/mortality in patients with chronic kidney disease (CKD) are uncertain and sometimes contradictory. The aims of our study were to determine the associations among different measures of obesity and adiposity, and the risk of all-cause mortality or dialysis entry in stage 3-5 CKD patients.

MATERIALS

this observational cohort study included 178 CKD patients followed for a median of 71 months. Biochemistry, anthropometric measures such as body mass index (BMI), waist-to-hip ratio, mid-arm muscle circumference (MAMC) and body composition by bioimpedance analysis were evaluated.

RESULTS

we found a weak agreement between BMI and other measures of adiposity. In multivariable regression analysis, all measures of obesity such as BMI, waist circumference and waist-to-height ratio were not associated with dialysis entry and/or mortality. Instead, MAMC was associated with dialysis entry HR 0.82 [95% CI: 0.75-0.89] and high FM% with mortality HR 2.08 [95% CI: 1.04-4.18].

CONCLUSIONS

in our CKD population, lower MAMC was predictive of dialysis commencing, while a higher percentage of fatty mass was a predictor of mortality. Instead, obesity, as defined by BMI, is not associated with dialysis commencing or all-cause mortality.

Obesity and long-term outcomes after incident stroke: a prospective population-based cohort study

BACKGROUND

The association between obesity, major adverse cardiovascular events (MACE), and mortality in patients with incident stroke is not well established. We assessed the relationship between body mass index (BMI) and MACE in patients with incident stroke.

METHODS

The population-based cohort study identified 30 702 individuals from the Clinical Practice Research Datalink (CPRD GOLD) and Hospital Episode Statistics (HES) databases from the United Kingdom. Individuals were aged ≥18 years with incident stroke between 1-1-1998 and 31-12-2017, a BMI recorded within 24 months before incident stroke, and no prior history of MACE. BMI was categorized as underweight (<18.5 kg/m² ), normal (18.5-24.9 kg/m² ), overweight (25.0-29.9 kg/m² ), obesity class I (30.0-34.9 kg/m² ), class II (35.0-39.9 kg/m² ) and class III (≥40 kg/m2). MACE was defined as a composite of incident coronary heart disease, recurrent stroke, peripheral vascular disease (PVD), heart failure, and cardiovascular-related mortality. Multivariable Cox regression was used to assess differences in MACE risk between BMI categories.

RESULTS

At baseline, 1217 (4.0%) were underweight, 10 783 (35.1%) had a normal BMI, 10 979 (35.8%) had overweight, 5206 (17.0%) had obesity Class I, 1749 (5.7%) Class II, and 768 (2.5%) Class III. In multivariable analysis, higher BMI were associated with lower risk of subsequent MACE [overweight: HR 0.96, 95% CI 0.93-0.99)]; PVD [overweight: 0.65 (0.49-0.85); obesity Class III: 0.19 (0.50-0.77)]; cardiovascular-related death [overweight: 0.80 (0.74-0.86); obesity Class I: 0.79 (0.71-0.88); Class II: 0.80 (0.67-0.96)]; and all-cause mortality [overweight: 0.75 (0.71-0.79); obesity Class I: 0.75 (0.70-0.81); Class II: 0.77 (0.68-0.86)] when compared to those with normal BMI. The results were similar irrespective of sex, diabetes mellitus, smoking or cancer at time of incident stroke.

CONCLUSIONS

In patients with incident stroke, overweight or obesity were associated with a more favourable prognosis for subsequent MACE, PVD, and mortality, irrespective of sex, diabetes mellitus, smoking, or cancer at baseline. As with other cohort studies, our study demonstrates an association. Randomized control trials should be considered to robustly evaluate the impact of weight management recommendations on subsequent cardiovascular outcomes in stroke survivors.

Influence of Diabetic Retinopathy on the Relationship Between Body Mass Index and Mortality in Patients with Poorly Controlled Type 2 Diabetes

PURPOSE

An "obesity paradox" has been observed in patients with type 2 diabetes. However, the optimal body mass index (BMI) for survival may be influenced by the stage of diabetes. We examined the relationship between BMI and mortality in patients with type 2 diabetes and the influence of diabetic retinopathy (DR).

PATIENTS AND METHODS

This is a retrospective cohort composing patients with type 2 diabetes who were admitted due to poor glucose control. Presence of DR was confirmed by ophthalmologists. The primary outcome was all-cause mortality. The association between BMI and mortality was assessed using a Cox proportional hazards model with adjustment for age, sex, and traditional risk factors.

RESULTS

A total of 2053 patients were enrolled. Over median follow-up of 6.7 years, there were 1060 deaths. Patients were classified into five categories based on admission BMI (kg/m²): <18.5, 18.5‒23, 23‒25, 25‒27 (reference), 25‒30 and >30. Mortality risk was significantly higher in the <18.5 kg/m², 18.5-23 kg/m², and 23-25 kg/m² categories than in the reference category (P <0.001). The similar obesity paradox was observed in the subgroup of patients without DR. However, in patients with DR, only patients with BMI <18.5 kg/m² had significantly increased mortality than those in the reference category. The presence of DR significantly modified the shape of the association between BMI and mortality (P = 0.019).

CONCLUSION

The obesity paradox exists in patients with poorly controlled type 2 diabetes. The presence of DR appears to significantly influence the shape of the association between BMI and mortality.

Predicted lean body mass, fat mass, and all cause and cause specific mortality in men: prospective US cohort study

OBJECTIVE

To investigate the association of predicted lean body mass, fat mass, and body mass index (BMI) with all cause and cause specific mortality in men.

DESIGN

Prospective cohort study.

SETTING

Health professionals in the United States PARTICIPANTS: 38 006 men (aged 40-75 years) from the Health Professionals Follow-up Study, followed up for death (1987-2012).

MAIN OUTCOME MEASURES

All cause and cause specific mortality.

RESULTS

Using validated anthropometric prediction equations previously developed from the National Health and Nutrition Examination Survey, lean body mass and fat mass were estimated for all participants. During a mean of 21.4 years of follow-up, 12 356 deaths were identified. A J shaped association was consistently observed between BMI and all cause mortality. Multivariable adjusted Cox models including predicted fat mass and lean body mass showed a strong positive monotonic association between predicted fat mass and all cause mortality. Compared with those in the lowest fifth of predicted fat mass, men in the highest fifth had a hazard ratio of 1.35 (95% confidence interval 1.26 to 1.46) for mortality from all causes. In contrast, a U shaped association was found between predicted lean body mass and all cause mortality. Compared with those in the lowest fifth of predicted lean body mass, men in the second to fourth fifths had 8-10% lower risk of mortality from all causes. In the restricted cubic spline models, the risk of all cause mortality was relatively flat until 21 kg of predicted fat mass and increased rapidly afterwards, with a hazard ratio of 1.22 (1.18 to 1.26) per standard deviation. For predicted lean body mass, a large reduction of the risk was seen within the lower range until 56 kg, with a hazard ratio of 0.87 (0.82 to 0.92) per standard deviation, which increased thereafter (P for non-linearity <0.001). For cause specific mortality, men in the highest fifth of predicted fat mass had hazard ratios of 1.67 (1.47 to 1.89) for cardiovascular disease, 1.24 (1.09 to 1.43) for cancer, and 1.26 (0.97 to 1.64) for respiratory disease. On the other hand, a U shaped association was found between predicted lean body mass and mortality from cardiovascular disease and cancer. However, a strong inverse association existed between predicted lean body mass and mortality from respiratory disease (P for trend <0.001).

CONCLUSIONS

The shape of the association between BMI and mortality was determined by the relation between two body components (lean body mass and fat mass) and mortality. This finding suggests that the "obesity paradox" controversy may be largely explained by low lean body mass, rather than low fat mass, in the lower range of BMI.