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FNOA: Assessment of Overweight/Obesity (2012)

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

To evaluate yearly, over a two-year period, age-related changes in body composition and fat distribution in a sample of elderly subjects and to evaluate the effect of sex on body composition and fat distribution changes after adjustment for physical activity, hormones and serum albumin.

Inclusion Criteria:

Subjects were eligible if they were able to walk at least 1/2 mile without difficulty and if they had no cognitive impairment (Mini-Mental State Examination score over 24).

Exclusion Criteria:

Exclusion criteria included:

  • Participation in regular physical exercise more than once a week during the study period
  • Renal insufficiency
  • Disabling knee osteoarthritis
  • Heart failure (New York Heart Association class 2 or higher)
  • Serious lung disease
  • Weight-loss greater then 5% over the last year.
Description of Study Protocol:
  • Recruitment: Subjects were randomly selected from the list of 11 general practitioners in the city of Verona, in order to have a good geographical representation of the city
  • Design: Prospective cohort study 
  • Blinding used: Implied with measurements.

Statistical Analysis

  • A repeated-measures analysis of variance was used to evaluate longitudinal changes in body composition and fat distribution in both sexes
  • Post-hoc analyses were performed using a Bonferroni correction
  • Between-sex comparisons of changes in body composition and fat distribution were performed using covariance analysis after adjustment for physical activity, hormones and serum albumin
  • When a significant difference between sexes was still observed in any body composition variables, its baseline value was added as covariate in the covariance analysis
  • A significance level of 0.05 was used throughout the study.
Data Collection Summary:

Timing of Measurements

  • Anthropometric measurements, body composition and clinical status were evaluated at baseline and yearly for two years
  • Physical function and biochemical measures were evaluated at baseline.

Dependent Variables

Anthropometric variables:

  • Body weight
  • Height
  • Body mass index (BMI)
  • Waist circumference
  • Hip circumference
  • Waist-to-hip ratio
  • Thigh circumference.
  • Dual Energy X-ray Absorptiometry (DXA)
    • Total body fat
    • Lean body mass (LBM)
    • Arm muscle
    • Leg muscle
    • Bone mineral content (BMC)
    • Appendicular skeletal muscle mass (ASM)
    • ASM adjusted by stature index (ASM/height2).

Independent Variables

Male or female.

Control Variables

  • Health status: Chronic diseases including cardiovascular disease, lung disease (emphysema, chronic bronchitis, asthma and other), degenerative joint disease, hypertension, intentional and unintentional weight loss
  • Physical function score, based on the Short-Form 36 Health Survey Questionnaire.

Biochemical Measures

  • Free testosterone concentration
  • IGF-concentration
  • Serum albumin.
Description of Actual Data Sample:
  • Initial N: 274
  • Attrition (final N): 161
  • Age: 68 to 78 years
  • Ethnicity: Italian
  • Other relevant demographics: 101 women and 60 men
  • Anthropometrics: Baseline BMI, 26.6±4.6 for women and 27.4±3.3 for men
  • Location: Verona, Italy.
Summary of Results:

Key Findings

Baseline data and sex

  • Age, BMI, serum albumin and IGF-1 levels were not significantly different between the sexes
  • Free testosterone levels were significantly higher in men than women (respectively, 8.69±6.03ng per ml and 1.97±2.90ng per ml; P<0.001)
  • Estimated level of physical activity was also significantly higher in men than women (respectively, 86.91±11.11 and 76±20.49; P<0.01).

Anthropometric variables at baseline and after one and two years

  • No significant changes in body weight were observed throughout the study
  • There was a significant decrease in height (P<0.001) and increases in BMI (P<0.01), waist circumference (P<0.001) and hip circumference (P<0.05)
  • There were no significant changes in WHR and thigh circumference significantly decreased (P<0.001).

Mean values for changes in body composition variables after one and two years of follow-up for women

  • Significant increases in total body fat (P=0.012) and percentage body fat (P=0.024) were observed, but LBM did not change throughout the study
  • Significant decreases in leg muscle mass (P<0.001), BMC (P<0.001) and ASM (P<0.001) were observed.

Mean values for changes in body composition variables after one and two years of follow-up for men

  • No significant changes in total body fat, percentage of body fat or LBM were observed throughout the study
  • Significant decreases in leg muscle mass (P<0.001), ASM (P<0.001), ASM/height2 (P<0.001) and BMC (P<0.001) were observed at the two-year follow-up.

Comparisons of changes in body composition variables from baseline to the two-year follow-up between men and women

  • The rate of loss in leg muscle mass and ASM was significantly greater in men than women (respectively, P=0.016 and P=0.008)
  • However, when the baseline values of leg muscle and ASM, respectively, were added as covariates, sex differences in the rate of loss of leg and ASM no longer existed.
Author Conclusion:

This two-year longitudinal study showed body composition and fat distribution changes in independently-living, weight-stable, elderly men and women. Leg muscle mass and ASM decreased, whereas waist circumference increased in both sexes. In men (but not in women), a significant decrease in the ASM-to-height2 ratio (a proposed proxy for sarcopenia) was found. The data also showed that the rates of loss of leg muscle mass and ASM were significantly greater in men than women. These findings are concurrent with those from other studies.

Another observation was a greater gender effect in muscle mass loss in men with a greater age-related loss of leg muscle mass and ASM. However, this difference was still significant after adjusting for physical activity, hormones and serum albumin, the strong influence of which on fat-free mass is well-known in both sexes. Moreover, the fact that any significant between-sex differences in leg muscle mass loss or ASM loss disappears, after adjusting respectively for the initial amounts of leg muscle and ASM, is consistent with another study. This suggests that the initial amount of leg muscle mass is the main predictor of its loss. It has been shown that women, compared with men of the same age, have an accelerated loss of muscle mass at the time of menopause: Thus, it is possible to hypothesize that the findings of a greater loss of muscle mass in elderly men than in women may depend on an attenuation of muscle decline in women in this age range.

This study also showed an increase in waist circumference in healthy elderly over a short period of time. This increase is a recognized proxy for abdominal fat, which is associated with cardiovascular risk factors, even in old age. The results of this study expanded those of previous studies showing re-distribution of body fat with aging in stable-weight subjects.

Funding Source:
Other: Not reported
Reviewer Comments:

The authors note the following limitations:

  • Only DXA was used to evaluate body composition changes and circumference measures to evaluate fat distribution changes. Instead of using a surrogate measure of visceral fat, such as waist circumference, more than one method should perhaps be applied to evaluate different components of body composition, as well as to determine visceral fat using imaging methods. However, DXA has successfully been validated as a body composition measurement instrument in the elderly and waist circumference has been recommended as an indicator of abdominal fatness in old age.
  • A two-year follow-up study can only provide a limited amount of information and longer follow-ups are necessary in the future to obtain more conclusive results
  • Adjustments were only performed for baseline hormone levels, physical activity and serum albumin because no information about their changes during the two-year follow-up was available for the subjects. Moreover, this study cannot rule out the hypothesis that short-term changes in hormones, physical activity or serum albumin may be responsible for body composition changes rather than the aging process itself. Further studies with repeated measurements of items would be necessary to test the interrelationships between their changes and those of body composition.
  • The study population was limited to relatively healthy old men and women who thus cannot be considered as representative of a normal aging population
  • The sources of funding of the study were not provided.
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? 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? 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? 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? 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? ???
  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? ???
  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)? 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? ???
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? ???