EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate visceral fat mass in a cross-sectional study of healthy aging individuals and relate quantitative visceral fat mass to both age and insulin sensitivity.

Inclusion Criteria:

Community-dwelling
Ambulatory and normally active
Considered healthy by medical history, physical exam, ECG, complete blood count, routine blood and urine chemistries and thyroid function tests.

Exclusion Criteria:

Non-community dwelling
Non-ambulatory
Considered not healthy by medical history, physical exam, ECG, complete blood count, routine blood and urine chemistries and thyroid function test
Taking medication known to affect glucose metabolism, blood pressure or lipids
Demonstrated a diabetic response according to World Health Organization criteria during the oral glucose tolerance test.

Description of Study Protocol:

Recruitment: 60 healthy community-dwelling subjects between the ages of 23 and 83 completed the study. The study was designed to evaluate equal numbers of subjects in each decade who were at least 125% and less than 125% of the ideal body weight. The method of recruiting and sampling is not reported.
Design: Cross-sectional study
Blinding used: Implied with measurements
Intervention: None
Statistical analysis: Descriptive statistics and multivariate regression. In regression models, insulin sensitivity and intra-abdominal fat were examined both with and without transformation.

Data Collection Summary:

Timing of Measurements

After recruitment and signed consent was received, subjects underwent a physical exam which included quantification of intra-abdominal fat and subcutaneous abdominal fat masses by MRI; a 75-gram oral glucose tolerance test performed after a 12-hour fast with blood samples taken at 30, 60, 120 and 180 minutes after glucose ingestion; and insulin-sensitivity testing, using the frequently-sampled intravenous tolerance test, using exogenous insulin administration.

Dependent Variables

Insulin sensitivity (frequently sampled intravenous tolerance test with exogenous insulin administration).

Independent Variables

Intra-abdominal fat and subcutaneous abdominal fat (MRI)
Age.

Control Variables

BMI (calculated with measured height and weight).

Description of Actual Data Sample:

Initial N: 60 participants (15 men and 45 women)
Attrition (final N): All participants were included in the analysis
Age: Range, 23 years to 83 years
Ethnicity: Not reported
Other relevant demographics: Not reported
Anthropometrics: No significant difference was noted in BMI or weight, among the age categories at baseline (age categories: 20 to 40 years, 40 to 60 years, 60 to 80 years)
Location: Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina, USA.

Summary of Results:

Key Findings

No relationship was observed between age and insulin-sensitivity for men or women
BMI and weight did not increase with age in this cohort, however waist-to-hip ratio tended to increase with age in both men (R=0.43, P=0.11) and women (R=0.31, P=0.039)
Intra-abdominal fat, expressed as total area and total area per kilogram body weight, increased significantly with age in both men (R=0.58, P=0.022) and women (R=0.48, P=0.0008)
No association with age was noted for subcutaneous fat or total fat
Glucose tolerance was significantly related to age in men (R=0.60, P=0.019) and approached significance in women (R=0.29, P=0.056)
Associations of intra-abdominal fat with insulin-sensitivity were significant in both men (R=-0.68, P=0.0001) and women (R=-0.44, P=0.0024)
Associations of waist-to-hip ratio and insulin-sensitivity were only significant in women (R=0.57, P=0.001)
No correlation was found of the intra-abdominal fat ratio to insulin-sensitivity in either women or men
Intra-abdominal fat was significantly associated with the glucose AUC in both men (R=0.52, P=0.048) and women (R=0.44, P=0.0026)
Waist-to hip ratio was significantly associated with glucose AUC in women only (R=0.42, P=0.004).

Multivariate Analysis

Models including gender-fat interaction and log (intra-abdominal fat) explained 13% more of the variance in insulin-sensitivity than the model containing waist-to-hip ratio
Models including gender, age, fat measurements and gender-age interactions; the model including intra-abdominal fat accounted for 51% of the variance in insulin-sensitivity.

Author Conclusion:

Our data indicate that aging is associated with changes in body composition reflected by an increase in waist-to-hip ratio, but more notably by the accumulation of intra-abdominal fat. This accumulation of intra-abdominal fat occurred despite controlling for the association of body weight and BMI with age in this study.
The major finding of this study is that measures of body composition such as waist-to-hip ratio and intra-abodominal fat accounted for 28% and 51%, respectively, of the variance in insulin-sensitivity. Age accounted for approximately 1% of the variance.

Funding Source:

Government:	National Institutes of Health
University/Hospital:	Bowman Gray School of Medicine, Wake Forest University

Reviewer Comments:

The method of sampling and recruiting is unknown. The authors state that the study was designed to evaluate equal numbers of subjects in each decade who were at least 125% and less than 125% of ideal body weight. It is unknown how this was accomplished and whether the sampling method introduced bias.
No demographics were reported for the participants. The age range suggests that the study was open to participants of any age (perhaps limited to adults), but that is unknown.
Details of the statistical analysis performed are limited
Sample size differences in men and women may account for some of the non-significant findings with regard to waist-to-hip ratio and insulin-sensitivity in men than showed an overall significant trend. No power calculation was reported.

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?	No
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?	???
	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?	???
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.)	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?	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.)	Yes
	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?		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?		No
	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?	No
	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?		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?		???
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	No
	8.2.	Were correct statistical tests used and assumptions of test not violated?	???
	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?	No
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