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CKD: Energy Requirements (2001)


Kopple JD, Monteon FJ, Shaib JK.  Effect of energy intake on nitrogen metabolism in nondialyzed patients with chronic renal failure.  Kidney Int. 1986;29:734-742.


Worksheet created prior to Spring 2004 using earlier ADA research analysis template.
PubMed ID: 3702224
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to determine the energy requirements of patients with chronic renal failure not undergoing maintenance dialysis while consuming 0.55-0.60 g/kg protein.

Inclusion Criteria:

1. Chronic renal failure

2. Not undergoing chronic hemodialysis

Exclusion Criteria:
Not specifically mentioned.
Description of Study Protocol:

Recruitment: clinic patients, methods not specified.

Design:  Randomized Controlled Trial

Blinding Used (if applicable): not used - lab tests

Intervention: Subjects were randomly assigned to a diet containing either 45, 35, 25 or 15 kcal/kg/d and 0.55 to 0.60 g protein/kg/d; diets were supplemented with vitamins and minerals and sodium and water was adjusted for each subject to maintain fluid balance and control blood pressure. 

Statistical Analysis: student's unpaired t test, paired t test and linear regression.


Data Collection Summary:

Timing of measurements: Metabolic studies were carried out while subjects were in a clinical research center or a special diagnostic and treatment center at a VA hospital. Daily urine and blood collection, weekly feces, indirect calorimetry last day of study.

Dependent variables:

  • Nitrogen determinations were made from 24-hr urine, 7 day stool collections and duplicate diets
  • Serial determinations of anthropometric measurements
  • Energy expenditure (basal) was measured using indirect calorimetry at the end of each study at 7 a.m. at rest after a period of fasting 

Independent variables:

  • Diet containing either 45, 35, 25 or 15 kcal/kg/d and 0.55 to 0.60 g protein/kg/d
  • Diets were supplemented with vitamins and minerals and sodium and water was adjusted for each subject to maintain fluid balance and control blood pressure
  • Subjects maintained a prescribed amount of exercise several times/d on a treadmill or stationary bicycle

Control variables: Individual differences in response considered.

Description of Actual Data Sample:

Initial N:  16 different balance studies were carried out on 6 subjects (4 men and 2 women) with chronic kidney failure, not on maintenance hemodialysis.

Attrition (Final N):  6 subjects

Age: 56 +/- 6 years

Ethnicity:  4 Black, 1 White, 1 Asian

Other relevant demographics and anthropometrics:  see below


Baseline demographics of subjects:

Age, yr


Weight, kg


Serum creatinine, mg/dl


Serum urea nitrogen, mg/dl


Serum albumin, g/dl


Creatinine clearance, ml/min


Urea clearance, ml/min


Hematocrit, %


Location:  California

Summary of Results:

Other Findings:

The mean balance period was 23.7+5.7 days. Four subjects consumed a mean of 45.0+1.39 kcal/kg, 6 subjects consumed a mean of 34.9+0.27 kcal/kg, 6 subjects consumed a mean of 24.9+0.7 kcal/kg and 2 subjects consumed a mean of 15.2+0.35 kcal/kg.

Nitrogen balance studies: Nitrogen balance correlated significantly with energy intake (r=0.505, P<0.05).

Urinary nitrogen appearance (UNA) tended to be lowest with the 45 kcal/kg/d diet and correlated inversely with the energy intake (r = - 0.671, P<0.01).

The mean UNA was significantly decreased on 45 kcal/kg/d than 25 kcal/kg/d (P<0.05) or the 25 and 15 kcal/kg/d intakes combined (P<0.05).

The mean UNA was significantly decreased on 45 kcal/kg/d and 35 kcal/kg/d combined than the 25 and 15 kcal/kg/day intakes combined (P<0.05).

There was an inverse correlation between postabsorptive plasma concentrations of several amino acids (especially essential amino acids) and dietary energy intake (P<0.05).

There was a positive correlation between change in edema free body weight and energy intake (r = 0.542, P<0.05).

Based on the basal energy expenditure measurements and adding 1.6 to 1.7 kcal above basal for mild to moderate activity, the mean total energy requirements for the 6 subjects was 29.1+ 8.4 kcal/kg/d ranging from 18.4 to 39.2 kcal/kg/d with the lowest value in one of the women.

Author Conclusion:

The results of this study suggest that although some clinically stable nondialyzed chronically uremic patients ingesting 0.55 to 0.60 g protein/kg/d may maintain nitrogen balance with energy intakes <30 kcal/kg/d, a dietary intake providing ~35 kcal/kg/d is more likely to maintain neutral or positive nitrogen balance, maintain or increase body mass, and decrease net urea generation.

Since protein conservation and nitrogen balance tended to be greater with 45 kcal/kg/d, this energy intake may be preferable for nutritionally depleted patients.

Low energy intakes in individuals with chronic renal disease may represent anorexia and contribute to wasting and malnutrition that is frequently found in these patients.

Funding Source:
Government: NIH, Instituto Mexicano del Segure Social
University/Hospital: VA Wadsworth Medical Center
Foundation associated with industry:
Reviewer Comments:

Well-conducted study on a small sample of subjects. Overall, the results of the study support that the recommendations for energy requirements for individuals with chronic kidney disease (before dialysis) are similar to healthy individuals of the same age.  However in 3 of the 6 subjects requirements were less than the recommended range of 30-30 kcal/kg/d at 18.4, 21.2 and 26.5 respectively. 

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? ???
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes