Chronic Kidney Disease and the Adiposity Paradox: Valid or Confounded?

Fat tissue quantity, waist circumference or waist-to-hip ratio in patients with chronic kidney disease: A systematic review and meta-analysis

The BMI predicts mortality and cardiovascular disease (CVD) in the general population, while in patients with end-stage chronic kidney disease (CKD) a high BMI is associated with improved survival, a phenomenon referred to as the "obesity paradox". While BMI is easy to determine and helps to categorize patients, it does not differentiate between fat tissue, lean tissue and bone mass. As the BMI may be altered in CKD, e.g. by muscle wasting, we determined in this meta-analysis (i) the association of mortality with fat tissue quantity in CKD and (ii) the association of mortality with abdominal obesity (as measured by waist circumference (WC) or waist-to-hip ratio (WHR)) in CKD. We systematically reviewed databases for prospective or retrospective cohort studies. In eleven studies with 23,523 patients the association between mortality and high fat tissue quantity in CKD was calculated. The pooled hazard ratio (HR) for this association in the CKD group in the dialysis group 0.91 (CI 0.84- 0.98, p = 0.01) which is comparable to the HR for the association with BMI. The HR in patients without dialysis was 0.7 (95% CI 0.53- 0.93, p = 0.01), suggesting a better risk prediction of high fat tissue content with mortality as compared to higher BMI with mortality in patients with CKD without dialysis. Importantly, both BMI and fat tissue quantity in CKD are described by the "obesity paradox": the higher the fat tissue content or BMI, the lower the mortality risk. In thirteen studies with 55,175 patients the association between mortality and high WC or WHR in CKD (with or without dialysis) was calculated. We observed, that the HR in the WHR group was 1.31 (CI 1.08-1.58, p = 0.007), whereas the overall hazard ratio of both groups was 1.09 (CI 1.01-1.18, p = 0.03), indicating that a higher abdominal obesity as measured by WHR is associated with higher mortality in CKD. Our analysis suggests gender-specific differences, which need larger study numbers for validation. This meta-analysis confirms the obesity paradox in CKD using fat tissue quantity as measure and further shows that using abdominal obesity measurements in the routine in obese CKD patients might allow better risk assessment than using BMI or fat tissue quantity. Comparable to the overall population, here, the higher the WHR, the higher the mortality risk.

Body Mass Index and Clinical and Health Status Outcomes in Chronic Coronary Disease and Advanced Kidney Disease in the ISCHEMIA-CKD Trial

OBJECTIVE

This study aimed to assess whether an obesity paradox (lower event rates with higher body mass index [BMI]) exists in participants with advanced chronic kidney disease (CKD) and chronic coronary disease in the International Study of Comparative Health Effectiveness of Medical and Invasive Approaches (ISCHEMIA)-CKD, and whether BMI modified the effect of initial treatment strategy.

METHODS

Baseline BMI was analyzed as both a continuous and categorical variable (< 25, ≥ 25 to < 30, ≥ 30 kg/m2). Associations between BMI and the primary outcome of all-cause death or myocardial infarction (D/MI), and all-cause death, cardiovascular death, and MI individually were estimated. Associations with health status were also evaluated using the Seattle Angina Questionnaire-7, the Rose Dyspnea Scale, and the EuroQol-5D Visual Analog Scale.

RESULTS

Body mass index ≥ 30 kg/m2 vs < 25 kg/m2 demonstrated increased risk for MI (hazard ratio [HR] [95% confidence interval] = 1.81 [1.12-2.92]) and for D/MI (HR 1.45 [1.06-1.96]) with a HR for MI of 1.22 (1.05-1.40) per 5 kg/m2 increase in BMI in unadjusted analysis. In multivariate analyses, a BMI ≥ 30 kg/m2 was marginally associated with D/MI (HR 1.43 [1.00-2.04]) and greater dyspnea throughout follow-up (P < .05 at all time points). Heterogeneity of treatment effect between baseline BMI was not evident for any outcome.

CONCLUSIONS

In the ISCHEMIA-CKD trial, an obesity paradox was not detected. Higher BMI was associated with worse dyspnea, and a trend toward increased D/MI and MI risk. Larger studies to validate these findings are warranted.

Metabolic and histomorphological changes of adipose tissue in cachexia

PURPOSE OF REVIEW

To describe the role of the main changes occurring in adipose tissue during cachexia and how these affects patient's outcomes, with a specific focus on cancer.

RECENT FINDINGS

In cachexia, the changes within the adipose tissue have been recently described as the presence of inflammatory infiltration (T-lymphocytes and macrophages), enhanced fibrosis, and the occurrence of beige adipocytes (i.e., browning). The latter one is a process driving cachexia enhancing thermogenesis, primarily via modulation of uncoupling protein 1. Also, increased lipolysis of white adipose tissue, especially in cancer, via higher expression of hormone sensible and adipose tissue triglyceride lipases, was detected in experimental models and in human adipose tissue. Other systemic metabolic alterations occur in association with changes in adiposity, including insulin resistance and increased inflammation, all conditions associated with a worse outcome. Moreover, these profound metabolic alterations were shown to be implicated in several consequences, including extreme and progressive unvoluntary body weight loss.

SUMMARY

Alterations in adiposity occur early during cachexia. Adipose tissue atrophy, as well as metabolic changes of white adipose tissues were observed to be pivotal in cachexia, and to be implicated in several clinical complications and poor prognosis.Further research is necessary to clarify the mechanisms underlying the loss of adiposity and therefore to identify novel therapeutic options to counteract this phenomenon in cachexia.

The Association of Sarcopenia and Central Obesity with Mortality Risk in Patients with Chronic Kidney Disease - a 2-Year Observational Study

Background

Patients with chronic kidney disease (CKD) face numerous challenges regarding their nutritional status, including undernutrition, wasting, overweight, and obesity. However, there is a gap in the knowledge on the importance of nutritional status on the survival of CKD in patients along the spectrum of progression of CKD.

Objectives

This study aimed to investigate the association of several nutritional measures with all-cause mortality. The hypothesis was that indicators of nutritional status exceeding BMI are associated with increased mortality risk.

Methods

One-hundred seventy adult patients with predialysis CKD (n = 82), receiving hemodialysis (n = 42) or kidney transplantation (n = 46) were recruited from 2014 to 2019. At baseline, nutritional status was assessed by anthropometry, body composition, and muscle function by handgrip strength. Patient survival was assessed after a 2-y follow-up by Cox regression models adjusted for age, sex, and renal function and generalized additive models.

Results

Thirty-one patients (18%) died during the 2-y follow-up. Sarcopenia (n = 30) was associated with an increased risk of death (HR: 2.92; 95% CI: 1.24, 6.89), whereas central obesity (n = 82) was not associated with mortality (1.05; 0.51, 2.15) in the Cox regression analyses. An association between BMI and mortality risk per unit increase (0.97; 0.90, 1.05) was not observed. Other markers of nutritional status were inversely associated with mortality risk, including handgrip strength (0.89; 0.83, 0.95), mid-upper arm circumference (0.86; 0.78, 0.95), and phase angle (per 0.1 degree increase 0.86; 0.81, 0.92). In the generalized additive models, U-shaped relationships were observed between mortality risk and waist circumference and mid-upper arm muscle circumference, while BMI < 22 kg/m2 was associated with increased mortality risk.

Conclusions

Sarcopenia, but not central obesity was associated with total mortality in patients with CKD. The inclusion of muscle strength and mass measures in clinical practice should be considered.

Normal weight and waist obesity indicated by increased total body fat associated with all-cause mortality in stage 3–5 chronic kidney disease

Patients with chronic kidney disease (CKD) demonstrate a survival benefit with a high body mass index (BMI); this is the obesity paradox. Central obesity has a higher prognostic value than BMI, even in those with normal weight. Whether total body fat percentage (TBF%) provides more information than BMI and waist circumference (WC) remains unknown. We included 3,262 Asian patients with stage 3–5 CKD and divided these patients by TBF% and waist-to-height ratio (WHtR) quartiles (Q1–Q4). TBF% was associated with BMI, WC, nutritional markers, and C-reactive protein. In all patients, BMI but not TBF% or WHtR demonstrated a survival paradox. In patients with BMI &lt;25 kg/m2, but not in those with BMI ≥ 25 kg/m2, TBF% Q4 and WHtR Q4 were associated with all-cause mortality, with hazard ratios [HRs; 95% confidence intervals (CIs)] of 2.35 (1.31–4.22) and 1.38 (1.06–1.80), respectively. The HRs of TBF% Q4 for all-cause mortality were 2.90 (1.50–5.58) in patients with a normal WC and 3.81 (1.93–7.50) in patients with normal weight and normal WC (All P for interaction &lt; 0.05). In conclusion, TBF% can predict all-cause mortality in patients with advanced CKD and a normal weight, normal WC, or both.

The Effects of Oral Energy-Dense Supplements on Nutritional Status in Nondiabetic Maintenance Hemodialysis Patients: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Fat-based energy-dense nutritional supplements may offer benefits over protein- or carbohydrate-dense supplements for patients receiving dialysis because of the adverse metabolic consequences of the latter. We conducted a randomized controlled trial to assess the effects of the short-term use of a fat-based nutritional supplement on various measures of nutritional status in patients receiving maintenance hemodialysis who have low dietary energy intake.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We enrolled nondiabetic patients receiving hemodialysis for >3 months who had inadequate dietary energy intake (<30 kcal/kg per day). The participants were randomly assigned in a 1:1 ratio to receive an oral fat-based energy-dense supplement (300 kcal daily) or routine care for 12 weeks (n=120 per group). The primary outcome was the change in phase angle measured by bioelectrical impedance analysis, a marker of cell integrity and body cell mass, from the baseline to week 12. The secondary outcomes were changes in quality of life. Other outcomes included laboratory nutritional indicators and physical examinations.

RESULTS

The average age of the total population was 47 (SD: 12) years, and 55% were men. The median of dialysis vintage was 43.4 (22.5-76.3) months; 240 participants were randomly assigned to the intervention (n=120) or control group (n=120). In total, 228 (95%) participants completed the trial. The change in phase angle did not differ significantly between the intervention and control groups (estimate, 0.0; 95% confidence interval, -0.1 to 0.1 versus estimate, 0.0; 95% confidence interval, -0.1 to 0.1; estimated difference, 0.0; 95% confidence interval -0.2 to 0.2; P=0.99). None of the 19 domains of quality of life differed between the groups. Adverse events were reported in 23 (19%) participants in the control group and 40 (33%) participants in the intervention group.

CONCLUSIONS

In nondiabetic patients on maintenance hemodialysis, short-term administration of fat-based energy-dense nutritional supplement has no clinically significant effect on nutritional status as measured by phase angle.

PODCAST

This article contains a podcast at https://https://www.asn-online.org/media/podcast/CJASN/2021_08_03_CJN16821020.mp3.

Impact of obesity on influenza compared to pneumonia hospitalization outcomes

OBJECTIVES

Previous literature has suggested that obesity impacts mortality risk differently in bacterial versus viral infections. This study sought to further elucidate this association in pneumonia versus influenza.

DESIGN

Retrospective cohort study.

SETTING AND PARTICIPANTS

Data were collected from the US Nationwide Readmission Database from 2013 to 2014.

METHODS

Patients were categorized into three weight groups: normal weight (BMI 18.5-25.0 kg/m²), obese (BMI 30-40.0 kg/m²), and morbidly obese (BMI ≥ 40 kg/m²). To minimize confounding, we excluded patients with a history of smoking, alcoholism, or chronic wasting conditions, as suggested by the Global BMI Mortality Collaboration. To further isolate obesity from baseline differences across cohorts, we performed a three-way propensity matching analysis. The association between body weight and in-hospital all-cause 30-day mortality was assessed using Cox proportional hazard regression analysis.

RESULTS

132,965 influenza and 34,177 pneumonia hospitalizations were identified. For patients with influenza, obesity (hazard ratio [HR]: 1.51; 95% CI: 1.01-2.26) and morbid obesity (HR: 1.64; 95% CI: 1.10-2.44) were associated with higher in-hospital 30-day mortality compared to normal weight. For pneumonia, obesity (HR, 0.41; 95% CI, 0.20-0.84) and morbid obesity (HR, 0.49; 95% CI, 0.25-0.96) were associated with reduced 30-day mortality compared to normal weight.

CONCLUSIONS AND IMPLICATIONS

Obesity may increase 30-day mortality risk during influenza hospitalization but provide mortality benefit in pneumonia, a divergent effect not adequately explained by lower admission threshold.

Hand Grip and Leg Muscle Strength in Hemodialysis Patients and Its Determinants

BACKGROUND

Chronic kidney disease is associated with chronic inflammation and progressive loss of peripheral muscle strength and the ability to exercise, and these changes are highly pronounced in patients receiving hemodialysis (HD). We evaluated hand grip strength (HGS) and leg muscle strength (LMS) in patients receiving HD and attempted to identify factors associated with muscle strength.

METHODS

We screened HGS (opposite the fistula side) and LMS (both sides) in HD patients at a single center (n = 112) by using digital hand and leg dynamometers (T.K.K. 5401 and 5710e/5715, Takei Scientific Instruments Co. Ltd., Niigata, Japan).

RESULTS

The mean age of patients was 62.6 years, and 73.2% of the patients were male. Diabetes was the cause of kidney failure in 50% of the patients, and the median HD vintage was 34 months. A total of 77.7% of patients reported that they participated in regular home-based exercise, and 29.5% of patients regularly participated in hospital-based resistance exercise. HGS and LMS showed good correlation (r = 0.715, P < 0.001). HGS (25.1 vs. 17.0 kg) and LMS (30.1 vs. 20.4 kg) were greater in males (P < 0.001 and P < 0.001, respectively) than in females. Older patients (≥ 60 years) showed less LMS than younger patients in both males and females (P = 0.012 and P = 0.037, respectively), but HGS did not differ according to age. Patients performing regular home- or hospital-based exercise showed higher HGS than those who did not exercise (24.2 vs. 18.6 kg, P = 0.011), but LMS was not significantly different (29.3 vs. 23.6 kg, P = 0.185). Multiple linear regression analysis proved that male sex, younger age, and any type of exercise were factors associated with improved HGS and LMS. Groups of older age (≥ 60 years), male sex, and shorter duration of HD (< median) benefitted more from exercise.

CONCLUSION

Sex, age, and exercise were the most important determinants of muscle strength in HD patients. We need to encourage patients to engage in regular home or group exercise from the beginning of dialysis and introduce new feasible forms of exercise for HD patients.

Under-Recognizing Malnutrition in Hospitalized Obese Populations: The Real Paradox

PURPOSE OF REVIEW

Obesity and malnutrition are frequently encountered in the hospitalized population. Although malnutrition associated with low or normal body mass index (BMI) is easily identified, malnutrition in obese patients goes frequently unrecognized as their fat mass masks underlying muscle mass deterioration. The purpose of this review is to explore if malnutrition has been studied in the obese hospitalized population and if that may be one of the reasons for the variable results in the obesity outcome data.

RECENT FINDINGS

Various studies have shown a conflicting association between obesity and outcomes in hospitalized patient population. Most prior studies used BMI alone as an indicator of obesity and although some recent studies have included body fat percentage, muscle mass, and functional status, they still showed variable outcomes. Unfortunately, there are not many studies that looked into nutrition status specifically in obese patients to study the outcomes. Studies evaluating clinical outcomes in obese patients showed a wide range of outcomes; some showed a protective effect while others were neutral. We explored recent data about obesity, malnutrition, and outcomes, where researchers more precisely defined malnutrition and obesity to determine health outcomes.

Epidemiology and outcomes of obese critically ill patients in Australia and New Zealand

OBJECTIVE

The apparent survival benefit of being overweight or obese in critically ill patients (the obesity paradox) remains controversial. Our aim is to report on the epidemiology and outcomes of obesity within a large heterogenous critically ill adult population.

DESIGN

Retrospective observational cohort study.

SETTING

Intensive care units (ICUs) in Australia and New Zealand.

PARTICIPANTS

Critically ill patients who had both height and weight recorded between 2010 and 2018.

OUTCOME MEASURES

Hospital mortality in each of five body mass index (BMI) strata. Subgroups analysed included diagnostic category, gender, age, ventilation status and length of stay.

RESULTS

Data were available for 381 855 patients, 68% of whom were overweight or obese. Increasing level of obesity was associated with lower unadjusted hospital mortality: underweight (11.9%), normal weight (7.7%), overweight (6.4%), class I obesity (5.4%), and class II obesity (5.3%). After adjustment, mortality was lowest for patients with class I obesity (adjusted odds ratio, 0.78; 95% CI, 0.74- 0.82). Adverse outcomes with class II obesity were only seen in patients with cardiovascular and cardiac surgery ICU admission diagnoses, where mortality risk rose with progressively higher BMIs.

CONCLUSION

We describe the epidemiology of obesity within a critically ill Australian and New Zealand population and confirm that some level of obesity is associated with lower mortality, both overall and across a range of diagnostic categories and important subgroups. Further research should focus on potential confounders such as nutritional status and the appropriateness of BMI in isolation as an anthropometric measure in critically ill patients.