FNOA: Assessment of Overweight/Obesity (2012)

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

To evaluate the relationship between body composition and physical performance.

Inclusion Criteria:

Inclusion criteria included:

  • The ability to walk at least 1/2 mile without difficulty
  • Free of cognitive impairment as measured by a Mini-Mental Status Examination.
Exclusion Criteria:

Exclusion criteria included:

  • Physical disability
  • Cognitive impairment
  • Congestive heart disease
  • Lung disease.
Description of Study Protocol:
  • Recruitment: Subjects were recruited from the lists of 11 general practitioners in the city of Verona. About 20 women were randomly selected from each general practitioner.
  • Design: Cross-sectional study
  • Blinding used: Implied with measurements.
Statistical Analysis
  • Comparisons between disabled and non-disabled women were made using the Student's T-test for unpaired data to compare differences between the mean (± standard deviation) of the two groups
  • Subjects were categorized by tertile of strength of the dominant leg
  • Covariance analysis was used to adjust anthropometric and body composition variables between women with and without disability for the disease variables and body mass index (BMI)
  • Covariance analysis was also used to adjust for BMI the association of tertiles of strength of the dominant leg with anthropometric and body composition variables
  • Coefficient of variation (CV) was computed by dividing the square root of the within-subject variance by the overall mean value of the measurement
  • Excluding two very obese subjects with BMIs of 43 and 50 from the statistical analysis did not change the results and therefore these women were included
  • Differences of P<0.05 were considered statistically significant.
Data Collection Summary:

Timing of Measurements

One-time measurement of the variables.

Dependent Variables

  • Distance walked during a six-minute walking test
  • Isometric strength of the knee extensors of the dominant leg.

Independent Variables

Body composition including:

  • Anthropometry: Weight, height, BMI, waist circumference, hip circumference, waist-to-hip ratio, sagittal diameter (SAD)
  • Bioelectrical impedance analysis (BIA): Body cell mass (BCM)
  • Dual energy X-ray absorptiometry (DXA): Total body fat, total fat-free mass tissue (FFM), percentage total fat
  • Reported disability: No physical function limitations, with physical limitations.

Control Variables

Chronic conditions including: Cardiovascular disease, lung disease (emphysema, chronic bronchitis, asthma, other), degenerative joint disease and hypertension.

Description of Actual Data Sample:
  • Initial N: 188 women initially selected
  • Attrition (final N): 144 women participated after application of exclusion criteria
  • Age: 68 to 75 years
  • Ethnicity: Italian
  • Anthropometrics: 63 subjects reported disability, 81 subjects were free of disability
  • Location: Verona, Italy.
Summary of Results:

Key Findings

  • Body weight, BMI, waist and hip circumferences, SAD, total body fat mass, leg fat mass and fat percentage were significantly higher in women with disability than in those considered normal
  • BCM-to-FFM ratio was significantly lower in women with disability than in those considered normal
  • The distance walked during the six-minute walking test was not significantly different between the two groups, but the leg strength, as assessed by a hand-held dynamometer, was significantly higher in normal women compared with those with disability
  • Because chronic diseases may themselves be responsible for disability, the percentage of subjects without disease or not affected by hypertension, lung disease, osteoarthritis and cardiovascular disease has been compared between normal women and those with disability
  • The percentage of normal women without disease was significantly higher than the percentage of women with disability without disease (respectively, 39% vs. 9%; P<0.05)
  • No significant differences in hypertension, cardiovascular disease and lung disease were found between normal women and those with disability, whereas osteoarthritis was significantly more prevalent in women with disability than in normal women (52% vs. 26%; P<0.005).
  • After adjustments for BMI and disease variables, no significant differences were found between the two groups regarding age, body weight, waist, hip, SAD, FFM, leg fat-free mass and BCM/FFM, whereas fat mass and leg fat mass were still significantly higher in women with disability than in normal women
  • Muscle strength of the dominant leg was significantly higher in normal women
  • When sub-dividing for tertiles of muscle strength after adjusted for BMI, women in the lowest tertile of muscle strength had significantly lower BCM, compared with those in the highest tertile
  • The percentage of disabled subjects was significantly higher in the lowest tertile than in the middle and highest tertiles (63.3% in the lowest tertile vs. 33.3% in the middle and highest tertiles, respectively; P<0.01).
Author Conclusion:

This cross-sectional study showed that high BMI values were associated with disability in older women, as are higher values of body fat and body fat percentage. The data also showed that disability was associated with lower leg strength. These results, showing a strong relationship between BMI and and disability, confirm and complement previous data but also expand this research by examining the direct effects of body composition.

Disability is predictive of mortality and thus the association of overweight and obesity with disability in older age seems to be clinically relevant. The results of this study showing a higher amount of total fat mass and leg fat mass in subjects with reported disability, but no difference in both total FFM and leg muscle mass between the two groups are consistent with the findings of another study. The data from several studies in very different populations seem to contradict the hypothesis that age-dependent loss of muscle mass may play a significant role in the decline of physical function.

It is important to consider several factors that may influence the relationship between muscle mass and disability:

  • It has been suggested that recent decline of muscle mass related to weight loss in persons with lower BMI may explain a significant increase of disability in older people. Only five women experienced a body weight decrease in the year before examination, so this did not apply to this study.
  • It is also possible that subjects with low BMI are frail and develop sarcopenia from disuse and will be at risk of disability. Only three women had BMI values below 19, so this did not apply to this study.
  • Body cell mass, as well as the ratio between BCM and FFM has been found to decrease with aging. This change may be one of the factors that increases the risk of disability in older people by changing the ability of the muscle to function even if the mass itself does not correlate with disability. In this study, the ratio between BCM and FFM was lower in women with disability and BCM showed a significant association with muscle strength. These results seem to suggest that muscle quality is an important determinant of muscle function.

In this study, higher values of waist circumference and sagittal diameter in in subjects with disability than those without were observed, but there was no association between these indices of fat distribution and the six-minute walking test or leg strength. The relationship between fat distribution and disability are unknown. Further studies using computed tomography or magnetic resonance imaging are needed to evaluate fat distribution.

This cross-sectional study showed that high BMI and total body fat are associated with disability in older women, whereas BCM was related to muscle strength. The ratio between BCM and FFM may be a good index of muscle quality related to its function. Future studies that include a wider sample of subjects of both sexes are needed in order to confirm these results.

Funding Source:
Government: Regione Veneto, Giunta Regionale, Ricerra Sanitaria Finalizzata, 730/01/96, Venezia, Italia, CNR Program on Aging, Padua, Italy, Office of Geriatric Epidemiology, Epidemiology, Demography and Biometry Program, National Institute of Health, National Institute of Aging, Bethesda MD
University/Hospital: Cattedra di Geriatria, Universita di Verona, Obesity Research Center, St. Luke's Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, Institute of Statistics, University of Trento, Trento, Italy
Reviewer Comments:

The authors note the following limitations:

  • The study sample was relatively small and examined only women in relatively good health
  • Because subjects were excluded that were unable to walk at least 1/2 mile, selection bias may have been introduced
  • It is possible to hypothesize that the older population in this study consisted of individuals whose fat-free mass was above a potential threshold, below which physical function was influenced negatively. Because of this, the data may not be representative of the general older population.
  • BCM was measured by BIA, using an equation adopted from Kotler. BIA is generally well-accepted as a method to evaluate body composition, but the Kotler equation was not developed in an older reference population. However, it has recently been observed that the accuracy of a BIA equation depends on the body composition of the population being evaluated rather than on age.

Only limited information was provided about the inclusion and exclusion criteria for the study.

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? No
  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? 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? No
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? No
  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? Yes
  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? Yes
  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? Yes
  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? 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? 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)? Yes
  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? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes