FNOA: Assessment of Overweight/Obesity (2012)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To investigate the bioelectrical characteristics in a large Caucasian group of apparently healthy men (age range, 50 to 80 years) as a function of age and body mass index (BMI).

Inclusion Criteria:
  • Complete population details of the The Olivetti Prospective Heart Study were described elsewhere
  • Participants were Caucasian men aged 50 to 80 years who were diet-free and did not follow a physical exercise program.
Exclusion Criteria:

Exclusion criteria were the presence of cancer, infection or any acute illness and irregular eating habits with poor dietary intake.

Description of Study Protocol:

Recruitment

Participants were examined in the framework of an ongoing prospective survey of cardiovascular risk factors on a working male population in southern Italy (The Olivetti Prospective Heart Study).

Design

Prospective cohort study.

Participants were divided into three groups according to BMI:

BMI  
18.5-24.9 Normal weight (NW)
25-29.9 Overweight (OW)
≥30 Obese (OB)

They were further stratified according to age:

Age  
50-59 Young-old (YO)
60-69 Old (O)
70-80 Oldest (OS)

Bioelectrical impedance vector analysis (BIVA) was used. This is a method of routinely monitoring changes in body composition based on assumption-free assessment of tissue hydration in any clinical condition. This method compares direct measurement of impedance vector with norms or average values derived from a reference healthy population (RXc graph method).

Blinding Used

Not used.

Statistical Analysis

  • The population sample under study provided at least 80% power to detect at P<0.05, a two-kg difference in body cell mass between each of the groups examined
  • Results were expressed as mean ±SD
  • Bonferroni post-hoc tests were used for the comparison among the three different age groups and among the three different BMI groups
  • Hotelling's T2 test was used for vector analysis
  • A P-value of less than 0.05 was considered statistically significant.

Impedance vector analysis

  • According to the RXc graph method, resistance and reactance measurements were normalized by the stature of subjects (i.e., R/H and Xc/H, expressed in ohsm per m)
  • Vectors were plotted as points on the gender-specific 50th, 75th and 95th tolerance ellipses, calculated from the reference healthy population
  • The vector's length (Z) was calculated according to the equation:
    [Z] = the square root of (R/H)2+(Xc/H)2 where R = Resistance, H = Height, Xc = Reactance
Data Collection Summary:

Timing of Measurements

Participants included in this analysis were consecutively seen during the first year of the 2002 to 2004 follow-up of the study. 

Dependent Variables

Bioelectrical characteristics including:

  • Resistance/height (R/H)
  • Reactance/height (Xc/H)
  • Phase angle (PA)
  • Vector length (VL)
  • Fat mass (FM)
  • Fat free mass (FFM)
  • Body cell mass (BCM).

Independent Variables

Age and BMI.

Description of Actual Data Sample:
  • Initial N: 315
  • Attrition (final N): 315
  • Age: 50 to 80 years
  • Ethnicity: Italian
  • Other relevant demographics: Male.

Anthropometrics

 
Age
BMI
Normal Weight
50-59
23.1±1.3
60-69
23.2±1.6
70-80
23.8±1.5
Overweight
50-59
27.3±1.5
60-69
27.3±1.4
70-80
27.1±1.1
Obese
50-59
32.3±1.8
60-69
32.3±2.2
70-80
32.7±3.1

Location

Southern Italy.

 

Summary of Results:

Key Findings

Anthropometric and bioelectrical parameters

  • BMI was not different in the YO, O and OS sub-groups within the NW, OW and OB categories
  • The stature-normalized R-values increased significantly, whereas phase angle and BCM decreased with age in the OW and OB groups
  • Considering BCM variations related to the increase in BMI, the YO sub-group had a significant BCM increase at higher BMI, while no significant differences were detected in the O and OS sub-groups. 

Frequency distribution of individual vectors

  • For each of the three BMI groups, in each age category, mean vector distributions were evaluated with vector bioelectrical impedance analysis (BIA)
  • Mean vector displacement followed a definite pattern with downward migration of the ellipses in OW and OB groups after 70 years of age
  • In both of these groups, mean vector displacement was significant as compared to OW and OB-YO groups, as documented by separate 95% confidence ellipses (P<0.05 i.e., significant Hotelling's T2 test)
  • With respect to the OW and OB-O groups, a significant smaller phase angle was observed in the OW and OB-OS groups, which allocated the lower half right of the 75% tolerance ellipse (6±1° vs. 6.7±1.8°, P<0.05; 6±0.08° vs. 6.9±1.4°, respectively)
  • Mean vector displacement and the phase angle were not significantly different for the NW-O, compared to the NW-OS group.
Author Conclusion:

The results of this study showed that after age 70, overweight and obese subjects present significant changes of bioelectrical parameters. In NW individuals, most vectors were still within the reference 75% tolerance ellipse, with some (9%) falling outside the lower half right of the 75% tolerance ellipse in older age groups (70 to 80 years). When OW and OB-OS groups were considered, a greater percentage (17% and 12.5%, respectively) of vectors fell outside the lower half of the 75% tolerance ellipse. As a result, in the OW and OB-OS groups only, there was a significant migration of the mean impedance vector to the right lower region of the RXc graph. Therefore, aging was associated with a pattern of vector BIA, indicating a decreased soft tissue mass (FFM and BCM), particularly in OW and OB-OS healthy men.

A significant reduction of BCM was observed in OW and OB-OS, as compared to OW and OB-YO groups. Sedentariness is often associated with obesity; it has been suggested that in obese subjects, reduced physical activity and a greater probability of functional limitation can affect FFM and BCM, with a notable impairment of OS. In this study, the YO group significantly increased BCM values were also detected at greater BMI. In the OS group, unchanged values of BCM were coupled with a higher BMI. In most obese individuals, the increment in fat mass is associated with a parallel increase in lean body mass, with each change accounting for almost half of the excess weight. Similarly, the YO group showed a proportional increment of BCM and FM. Therefore, particularly in obese people, it is possible that lifestyle and dietary habit modification are part of the cause of impaired BCM (sarcopenia), occurring with advancing age.

In summary, the changes in the bioelectrical impedance vector of healthy elderly individuals are associated with a decrease in soft tissue mass (FFM and BCM), particularly in overweight and obese men older than 70 years. Furthermore, in the present study, a different impedance vector pattern was associated with aging. The identification of this BIVA pattern may be useful for clinical purposes and, in particular, in geriatric routine to accurately assess changes in body composition and to compare obese patients and healthy subjects.

 

Funding Source:
Government: Institute of Food Science, National Research Council, Avelino, Italy
University/Hospital: University Federico II
Reviewer Comments:

The authors note the following limitations:

  • The bioelectrical impedance analysis (BIA) equations used are not completely specific for the age and BMI range of the subjects, which may have resulted in an overestimation of BCM in the obese category.
  • However, the limitation of the BIA method to evaluate body composition and its change can be overcome by the large size of the sample.

Other limitations include:

  • Detailed inclusion and exclusion criteria was provided elsewhere.
  • Only a population of men was studied.
  • Based on the design of the study of using information from another study, there were no withdrawals.  However, all participants were accounted for.
  • The author's affiliations were provided, but not study funding sources.
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? No
  2.2. Were criteria applied equally to all study groups? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? No
3. Were study groups comparable? ???
  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? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  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? No
  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%.) N/A
  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? No
  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.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  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? N/A
  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? 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? 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? No
  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)? No
  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? Yes
10. Is bias due to study's funding or sponsorship unlikely? ???
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? ???