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H/A: Caloric Needs (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To identify the relative contribution of changes in energy expenditure and intake to the pathogenesis of HIV-related weight loss.
Inclusion Criteria:
  • HIV infection: All subjects tested positive for HIV antibodies by ELISA and the Western blot assay
  • Controls were well, had stable weight and were at low risk for HIV infection.
Exclusion Criteria:
None specifically mentioned.
Description of Study Protocol:

Recruitment

  • Subjects recruited from two HIV clinics in London
  • Recruitment of controls not described.

Design

Case-control Study.

Intervention

51 assessments of energy metabolism were completed in 27 men with HIV infection at different stages of the disease, including periods of both rapid and slow weight loss. Also measured in healthy controls.

Statistical Analysis

  • Groups were compared by ANOVA with a post-hoc Scheffe test. When data from more than one study of a single man appeared in a group, a single mean value was used.
  • Linear regression was used to compare measurements of energy with the rate of weight change.
Data Collection Summary:

Timing of Measurements

Over course of two years, 51 assessments of energy metabolism were completed in 27 HIV-infected men at different stages of the disease, including periods of both rapid and slow weight loss. Also measured in healthy controls.

Dependent Variables

  • Resting energy expenditure was measured by indirect calorimetry
  • Total energy expenditure measured by the doubly-labeled water technique, not measured in controls 
  • Energy intake measured through weighed food records
  • Rate of weight loss or gain
  • Clinical history and physical examination
  • Height, weight, skinfold thicknesses
  • CBC and CD4 counts.

Independent Variables

HIV infection: Stage of infection determined according to criteria of Centers for Disease Control and Prevention.
Description of Actual Data Sample:
  • Initial N: 27 men with HIV infection, 12 healthy male controls
  • Attrition (final N): 27 cases, 12 controls
  • Age: Median age, 35 years; range 28 to 62 years. Controls aged 26 to 33 years.
  • Ethnicity: Not mentioned.
  • Anthropometrics: Controls matched for gender, but not age
  • Location: United Kingdom.

 

Summary of Results:

 

Rapid Weight Loss (>3 kg/Month)

Slow Weight Loss (<3 kg/Month)

 Stable Weight Weight Gain (>0.25 kg/Month)

P-Value
Number of Men 6 15 12 7 --

Number of Studies

7

21

 16 7

-- 

REE (kcal/kg/Day)

26.2±3.4

25.7±2.5

 25.0±1.8 30.1±2.8

0.001
TEE (kcal/kg/Day) 33.4±4.0 41.5±5.4 46.3±5.4 46.1±9.0 <0.001
Activity-Related (kcal/kg/Day) 7.2±3.7 15.8±5.6 21.2±5.4 16.0±7.4 <0.001
Energy Intake (kcal/kg/Day) 20.1±8.2 34.0±5.4 39.5±6.2 55.1±11.8 <0.001
Energy Balance (kcal/kg/Day) -13.3±8.7 -8.1±7.6 -6.6±8.0 8.0±5.2 <0.001

Other Findings

  • Resting energy expenditure, corrected for body mass, was higher by 9.6% in the HIV-infected men than in the normal men (P=0.002)
  • The mean total energy expended by the HIV-infected men was 2,750±670kcal per day, no more than that expended by normal men
  • There was a significant positive relation between total energy expenditure and the rate of weight change (R=0.61, P<0.001), thus during rapid weight loss, total energy expenditure was reduced to 2,180±580kcal per day (P=0.009), primarily because of reduced physical activity
  • During rapid weight loss, the negative energy balance (-850±580kcal per day) was primarily the result of the reduction in energy intake, to 1,330±610kcal per day, intake correlated strongly with the rate of weight change (R=0.84, P<0.001).
Author Conclusion:
The finding that total energy expenditure in HIV-infected men is not excessively high and is not increased during weight loss shows that the primary contributor to altered energy balance, and thus to weight loss in HIV infection, is decreased food intake. However, the prevention of weight loss or the promotion of weight gain and the recovery of body tissue, particularly skeletal muscle, after weight loss may require more than merely adequate energy intake, because energy supplied in the presence of active secondary infection may be preferentially deposited as fat rather than lean tissue. Thus, other interventions (for example, the administration of anabolic agents such as growth hormone) may be beneficial, but HIV-associated wasting can only be managed effectively in the presence of an adequate energy supply.
Funding Source:
Reviewer Comments:
  • Controls matched for gender but not age
  • Measurements made over a two-year period, other changes could have occurred during that time
  • Controls did not have all measurements completed.
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) N/A
  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) N/A
 
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? ???
  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? ???
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? No
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? No
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) No
  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.) No
  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? N/A
  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? Yes
  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? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  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? N/A
  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? ???
  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? No
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? Yes
  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? No
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