Abstract: SA-PO179

Diagnostic Discordance between Body Mass Index and Body Fat Percentage for Obesity among Patients with CKD

Session Information

Category: Nutrition, Inflammation, and Metabolism

  • 1401 Nutrition, Inflammation, Metabolism

Authors

  • Lin, Ting-yun, Teipai Tzu Chi Hospital, Taipei City, Taiwan
  • Hung, Szu-Chun, Teipai Tzu Chi Hospital, Taipei City, Taiwan
Background

In contrast to the general population, a higher body mass index (BMI) appears to be associated with a greater survival among patients with CKD, referred to as “obesity paradox”. This may be explained by limitation of BMI as a measure of adiposity in CKD. Both BMI and body fat percentage (BF%) are used to classify obesity but outcomes may vary.

Methods

We investigated the two different cutoffs for diagnosing obesity (BMI ≥28 kg/m2 or BF% >25% for male or >35% for female) and the impact on all-cause mortality in 326 nondialysis-dependent CKD patients with a median follow-up of 4.6 years. Body fat mass was determined using the Body Composition Monitor, a novel multifrequency bioimpedance spectroscopy device.

Results

Using BMI, 27.9% of patients were obese. However, 48.8% of patients were obese according to BF%. Although obesity defined by BMI was associated with a significantly lower risk of death, the result tended to be reverse when obesity was defined by BF%. When patients were classified into four distinct groups based on both BMI and BF% cutoffs for obesity, a considerable proportion of patients (29.4%) had excess body fat in the context of a normal BMI. These patients were more likely to have lower lean body mass and had higher mortality as compared to patients with obesity defined by both BMI and BF%.

Conclusion

Thus, diagnostic discordance between BMI and BF% may explain the “obesity paradox” because using BMI to detect obesity among those with CKD may miss a large number of patients with excess body fat. Proper diagnosis of obesity in patients with CKD is required for both risk prediction and treatment.

Cox models for relative risk of all-cause mortality calculated for obesity or not defined by BMI or BF%
CharacteristicsUnadjustedModel 1Model 2
HR (95% CI)P valueHR (95% CI)P valueHR (95% CI)P value
BMI-defined 
NonobeseReferenceReferenceReference
Obese0.26 (0.09–0.74)0.0120.32 (0.11–0.92)0.0340.26 (0.09–0.79)0.017
BF%-defined 
NonobeseReferenceReferenceReference
Obese1.93 (1.01–3.71)0.0471.55 (0.79–3.02)0.201.46 (0.73–2.90)0.282

Relationship of BF% versus BMI