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Recommendations Summary

CKD: Nutrition Assessment: Body Weight and Body Composition Usual-Care Statements (2020)

Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.


  • Recommendation(s)

    CKD: Body Composition and Body Weight/Body Mass Index (BMI)

    In adults with CKD 1-5D or posttransplantation, it reasonable to consider assessing body composition in combination with body weight/BMI at the first visit and to monitor overall nutrition status periodically over time (OPINION).

    Rating: Consensus
    Conditional

    CKD: Frequency of Body Weight/Body Mass Index (BMI) and Body Composition Assessment

    In adults with CKD 1-5D or posttransplantation who are clinically stable, it is reasonable to measure body weight and BMI and to monitor for changes in body weight/BMI and body composition as needed (OPINION).

    • At least monthly in MHD and PD patients
    • At least every 3 months in patients with CKD 4-5 or posttransplantation
    • At least every 6 months in patients with CKD 1-3 

    Rating: Consensus
    Conditional

    CKD: Assessment of Body Weight

    In adults with CKD 1-5D or posttransplantation, it is reasonable for a registered dietitian nutritionist (RDN) or an international equivalent or physicians to use clinical judgement to determine the method for measuring body weight (e.g. actual measured weight, history of weight changes, serial weight measurements, adjustments for suspected impact of edema, ascites and polycystic organs) due to absence of standard reference norms (OPINION).

    Rating: Consensus
    Conditional

    CKD: Body Mass Index (BMI) and Protein Energy Wasting (PEW)

    In adults with CKD 1-5D or posttransplantation, BMI alone is not sufficient to establish a diagnosis of PEW unless the BMI is very low (<18 kg/m2) (OPINION).

    Rating: Consensus
    Conditional

    • Risks/Harms of Implementing This Recommendation

      There are no obvious risks or harms associated with these recommendations.

    • Conditions of Application

      BMI

      • The standard weight status categories that have been defined by the WHO according to BMI ranges for adults should be used in the CKD population; these include <18.5 kg/m2 for underweight; 18.5 to 24.9 kg/m2 for normal weight; 25.0 to 29.9 kg/m2 for overweight; and ≥30 kg/m2 for obese. Population-specific BMI cut-offs to define weight status may be lower for Asain populations. 
      • BMI is not an ideal marker of obesity, since it cannot differentiate between higher weights due to increased adiposity vs. muscularity and it cannot identify visceral adiposity, which has negative metabolic effects. 
      • To ensure accuracy of BMI, height should be measured periodically. 
      • Limited evidence suggested that obesity (BMI ≥30 kg/m2) may be a risk factor for higher mortality in individuals who are on dialysis and under the age of 65. Therefore, practitioners should consider patient age when determining mortality risk according to BMI.

      Measuring Body Weight
      When using published weight norms in the anthropometric assessment of adult CKD patients, caution must be use as each norm has significant drawbacks.

      • Ideal body weight (IBW) is the body weight associated with the lowest mortality for a given height, age, sex and frame size and is based on the Metropolitan Life Insurance Height and Weight Tables. [Caution: Not generalizable to the CKD population and data-gathering methods were not standardized.]
      • Hamwi method can be used to estimate ideal body weight. [Caution: A quick and easy method for determining optimal body weight but has no scientific data to support its use.]
      • Standard Body Weight, NHANES II (SBW as per KDOQI Nutrition Practice Guidelines) describes the median body weight of average Americans from 1976 to 1980 for height, age, sex and frame size. [Caution: Although data is validated and standardized and uses a large database of ethnically-diverse groups, data is provided only on what individuals weigh, not what they should weigh in order to reduce morbidity and mortality.]
      • BMI often defines generalized obesity and CKD research, specific to dialysis patients, has identified that patients at higher BMIs have a lower mortality risk. [Caution: The researchers may not have statistically adjusted for all confounders related to comorbid conditions occurring in CKD on dialysis (diabetes, malignancy, etc.) and it is unclear how it may relate to CKD patients not on dialysis.]
      • Adjusted Body Weight (ABW) is based on the theory that 25% of the excess body weight (adipose tissue) in obese patients is metabolically active tissue. [Caution: This has not been validated for use in CKD and may either overestimate or underestimate energy and protein requirements.]

      Monitoring and Evaluation
      BMI should be used routinely to assess weight status in CKD patients since it is useful in predicting mortality.  However, in isolation, BMI is not sufficient to establish a diagnosis of PEW unless it is very low (<18 kg/m2)

    • Potential Costs Associated with Application

      There are no obvious costs associated with these recommendations

    • Recommendation Narrative

      Methods of assessing body composition, including anthropometric measurements, are components of the nutrition assessment in CKD.  Anthropometric measurements are practical, inexpensive and non-invasive techniques that describe body mass, size, shape, and levels of fatness and leanness; they are the most basic and indirect methods of assessing body composition.  These include height, weight, skinfolds, circumferences, bioelectrical impedance analysis (BIA) and creatinine kinetics.  Dual-energy X-ray absorptiometry (DXA) is a direct method that is considered the gold standard for assessing body composition in patients with CKD; however, this measure is labor intensive, invasive, expensive and can be influenced by a number of CKD related factors such as hydration status.

      Timing of body composition assessments is important in CKD since assumptions of hydration are required for accurate interpretation of the results, and fluid/electrolyte balance is likely to be altered significantly in CKD patients.  For these reasons, in adults undergoing dialysis, assessments are best obtained after treatment when body fluid compartments are in relatively normal interrelationship (Carrero et al 2015, Chumlea et al 2008).

      Regardless of the method selected to assess body composition, none are perfect, and the errors surrounding them should not be ignored.  Errors may have clinical relevance, especially if the individual is treated and observed over time (Chumlea et al 2008). Moreover, the results of the measures are only as useful as the availability of suitable reference data from a group of persons of at least the same age, race, gender and disease status.

      BMI should be used routinely to assess weight status in CKD patients since it is useful in predicting mortality (see BMI and mortality section).  However, in isolation, BMI is not sufficient to establish a diagnosis of PEW unless it is very low (<18 kg/m2).

    • Recommendation Strength Rationale

      The evidence supporting these recommendations  is based on Consensus/expert opinion evidence..

    • Minority Opinions

      Consensus reached.

  • Supporting Evidence

    The recommendations were created from the evidence analysis on the following questions. To see detail of the evidence analysis, click the blue hyperlinks below (recommendations rated consensus will not have supporting evidence linked).