Carrying a heavier weight is healthy: Obesity-reinforced fitness hypothesis in metabolically healthy obesity

The Obesity Paradox: A Nonlinear Relationship Between 30-Day Postoperative Complications and Body Mass Index After Total Shoulder Arthroplasty

BACKGROUND

An inverse relationship coined the "obesity paradox" has been propositioned, in which body mass index (BMI) may be contradictorily protective in patients undergoing surgery or treatment of chronic disease. This study sought to investigate the BMI associated with the lowest rate of medical complications after total shoulder arthroplasty (TSA).

METHODS

The American College of Surgeons National Surgical Quality Improvement Project database was queried to identify adults who underwent elective primary TSA between January 2012 and December 2020. Thirty-day postoperative medical complications were extracted, which included death, readmission, pneumonia, pulmonary embolism, renal failure, and cardiac arrest, among others. BMI was classified into five categories (underweight [BMI <18.5 kg/m 2 ], normal weight [BMI ≥18.5 and <25 kg/m 2 ], overweight [BMI ≥25 and <30 kg/m 2 ], obese [BMI ≥30 and <40 kg/m 2 ], and morbidly obese [BMI ≥40 kg/m 2 ]). We examined the risk of any 30-day postoperative complications and BMI categorically and on a continuous basis using multivariable logistic regression controlling for age, sex, procedure year, and comorbidities.

RESULTS

Of the 31,755 TSAs, 84% were White, 56% were female, and the average age of patients was 69.2 ± 9.3 years. Thirty-day postoperative medical complications occurred in 4.53% (n = 1,440). When assessed on a continuous basis, the lowest risk was in patients with a BMI between 30 and 35 kg/m 2 . Underweight individuals (BMI <18.5 kg/m 2 ) had the highest postoperative complication rates overall. The probability of medical complications increased with age and was greater for female patients.

CONCLUSION

The relationship between BMI and complication risk in TSA is nonlinear. A BMI between 30 and 35 kg/m 2 was associated with the lowest risk of medical complications after TSA, and BMI<18.5 kg/m 2 had the highest risk overall, indicating some protective aspects of BMI against 30-day medical complications. Thus, obesity alone should not preclude patients from TSA eligibility, rather surgical candidacy should be evaluated in the context of patients' overall health and likelihood of benefit from TSA.

LEVEL OF EVIDENCE

III, Retrospective Comparative Study.

Obesity, Chronic Kidney Disease, and Kidney Transplantation: An Evolving Relationship

Obesity has a fundamental role in driving the global kidney disease burden. The perplexing relationship of obesity with chronic kidney disease remains debated. However, a thorough understanding of the interplay of obesity in conjunction with chronic kidney disease and appropriate management options is lacking, leading to further increases in morbidity and mortality. Moreover, underutilization of bariatric procedures and unrealistic expectations of weight reduction based on body mass index, leading to poor access to kidney transplantation, are fueling the fire. In this review, we summarize the available data related to the obesity and chronic kidney disease association and its novel management options.

The Obesity Paradox: Body Mass Index Complication Rates Vary by Gender and Age Among Primary Total Hip Arthroplasty Patients

BACKGROUND

High body mass index (BMI) has long been recognized as a risk factor for postoperative complication among total hip arthroplasty (THA) patients. However, recent studies showed mixed results in the effect of high BMI on surgical outcomes. Our study is to examine the association of preoperative BMI with complication incidence, stratified by age and gender.

METHODS

We queried the American College of Surgeons National Surgical Quality Improvement Project database to identify patients who underwent elective primary THA between 2012 and 2016. We examined the associations between BMI as a continuous and a categorical variable and risk of 30-day postoperative complication, using 2 multiple polynomial logistic regression models. We also created predictive plots to graphically assess the relationship between BMI and complication by gender and age.

RESULTS

In total, 117,567 eligible patients were included in the analyses. The predictive probability of all-type postoperative complications showed a U-shaped relationship with continuous BMI values (range 10-65 kg/m²). The lowest complication risks occurred in patients with BMI between 35 and 40. Females had higher complication rate than males across all BMI values. This U-shaped relationship was only observed among patients younger than 60 years old, while the associations appear to be inversely linear among patients aged greater than 60 years.

CONCLUSION

Our results suggest that the current theory of a linear association between BMI and complication risk may not apply to elective primary THA. Strict BMI cutoffs may not minimize risk, especially among patients over 60 years old. Orthopedic surgeons should factor in patient-specific variables of age and gender when determining acceptable surgical risk given a particular BMI value.

Association of Body Mass Index and Outcome in Acutely Ill Patients With Chronic Kidney Disease Requiring Intensive Care Therapy

OBJECTIVE

An association of body mass index (BMI) and outcome, the "obesity paradox," has been described in patients with chronic kidney disease (CKD) and end-stage renal disease. We sought to assess whether a potential beneficial effect of a high body mass is also seen in CKD patients with critical illness.

METHODS

In a retrospective analysis of a prospectively collected database of 123,416 patients from 107 Austrian intensive care units (ICUs) in whom BMI was available, the association of 6 groups of BMI and hospital mortality was assessed in 12,206 patients with CKD 3-5 by univariate and multivariate logistic regression analyses.

RESULTS

Patients with CKD were sicker, had a longer ICU stay, and had a higher ICU and hospital mortality than those without. The association of BMI and outcome in CKD patients indicated a U-shaped curve with the highest mortality in patients with BMI <20 and ≥40, and the lowest with a BMI between ≥25 and <40. This relationship was also significant in a multivariate analysis adjusted for severity of illness assessed by Simplified Acute Physiology Score III score, age, gender, admission diagnosis, and pre-existing comorbidities. It was not found in patients with CKD 5 on renal replacement therapy, in patients below 60 years of age, and those with diabetes mellitus requiring insulin treatment.

CONCLUSIONS

BMI is associated with better outcomes in CKD 3-5 patients who have acquired acute intermittent diseases and are admitted to an ICU, but not those requiring renal replacement therapy. This higher tolerance to acute disease processes may in part explain the "obesity paradox" observed in CKD patients.

Mid-Arm Circumference and All-Cause, Cardiovascular, and Cancer Mortality among Obese and Non-Obese US Adults: the National Health and Nutrition Examination Survey III

Epidemiological studies have shown that mid-arm circumference (MAC) can be used to predict death risk and malnutrition. We performed a retrospective observational study involving 11,958 US participants aged 20–90 years from the National Health and Nutrition Examination Survey III, 1988–1994, to determine the correlation between MAC and all-cause, cardiovascular, and cancer mortality risk in the obese and non-obese population. Death certificate data were obtained up to 2006. The participants were divided into three groups on the basis of body mass index: 19 ≤ BMI < 25 kg/m² (normal weight group), 25 ≤ BMI < 30 kg/m² (overweight group) and BMI ≥ 30 kg/m² (obesity group); each group was then divided into three subgroups depending on their MAC level. In the non-obese population, MAC was inversely associated with all-cause mortality; specifically, in the normal weight group, the multivariate-adjusted hazard ratio of the T3 (29.6–42.0) cm subgroup was 0.72 (95% confidence interval: 0.58–0.90) when compared with the T1 (18.0–27.2) cm, while the multivariate-adjusted hazard ratio of the T2 (27.3–29.5) cm subgroup was 0.76 (95% confidence interval: 0.64–0.91) when compared with the T1 (18.0–27.2) cm subgroup. The results indicate that MAC is inversely associated with all-cause mortality in non-obese individuals in the United States.

The Obesity Paradox in Kidney Disease: How to Reconcile it with Obesity Management

Obesity, a risk factor for de novo chronic kidney disease (CKD), confers survival advantages in advanced CKD. This so-called obesity paradox is the archetype of the reverse epidemiology of cardiovascular risks, in addition to the lipid, blood pressure, adiponectin, homocysteine, and uric acid paradoxes. These paradoxical phenomena are in sharp contradistinction to the known epidemiology of cardiovascular risks in the general population. In addition to advanced CKD, the obesity paradox has also been observed in heart failure, chronic obstructive lung disease, liver cirrhosis, and metastatic cancer, as well as in the elderly. These are populations in whom protein-energy wasting and inflammation are strong predictors of early death. Both larger muscle mass and higher body fat provide longevity in these patients, whereas thinner body habitus and weight loss are associated with higher mortality. Muscle mass appears to be superior to body fat in conferring an even greater survival. The obesity paradox may be the result of a time discrepancy between competing risk factors, i.e., overnutrition as the long-term killer versus undernutrition as the short-term killer. Hemodynamic stability of obesity, lipoprotein defense against circulating endotoxins, protective cytokine profiles, toxin sequestration of fat mass, and antioxidation of muscle may play important roles. Despite claims that obesity paradox is a statistical fallacy and a result of residual confounding, the consistency of data and other causality clues suggest a high biologic plausibility. Examining the causes and consequences of the obesity paradox may help discover important pathophysiologic mechanisms leading to improved outcomes in patients with CKD.