EAL

FNOA: Assessment of Overweight/Obesity (2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate the relation between weight loss or weight gain and changes in lean mass and fat mass in older adults.

Inclusion Criteria:

Participant in The Health, Aging and Body Composition Study (Health ABC Study)
Age 70-79 years at cohort entry
Absence of difficulty with activities of daily living
Absence of difficulty walking a quarter of a mile or climbing 10 steps without resting.

Exclusion Criteria:

Recent treatment for cancer
Participation in a clinical trial
Intention to move out of the study area in a three-year timeframe.

Description of Study Protocol:

Recruitment

Recruited from a random sample of Medicare beneficiaries and through community-based recruitment of African American persons in designated ZIP codes in and around Pittsburgh, Pennsylvania and Memphis, Tennessee.

Design

Prospective cohort study

Blinding used

None

Intervention

Not applicable

Statistical Analysis

Differences in mean and proportions of baseline characteristics and body composition by sex were tested by using Student's t-tests and chi-square tests
Differences in mean changes in body composition by weight-change category and by sex within each weight-change category over the four-year period were tested by using ANOVA and t-tests
Analysis of covariance (ANCOVA) was used to ascertain the main effects of sex, race and weight-change category and the potential interactions between then on changes in total-body fat and lean mass over four years after controlling for potential confounders.

Data Collection Summary:

Timing of Measurements

Sociodemographic, lifestyle and health characteristics were measured at baseline by questionnaire and the cohort was monitored throughout the four-year follow-up period.

Dependent Variables

Total body weight
Total body bone-free lean mass
Total fat mass
Total body mass and body composition were measured at baseline and four-year follow-up by using fan-beam DXA.

Independent Variables

Weight status category (loss, stability or gain)
Net body weight change through the four-year period was calculated and subjects were grouped into three weight change categories: loss (≥3% of loss), stability (within 3% weight loss or gain) and gain (≥3% gain).

Control Variables

Sex
Age
Race
Interim hospitalizations
New weight change after hospitalization.

Description of Actual Data Sample:

Initial N: 3,075 men and women
Attrition (final N): 912 participants did not complete the full examination at follow-up
Age: 70-79 years at cohort entry (mean age 73.7±2.8 years for men and 73.3±2.8 years for women)
Ethnicity: 33.0% black (men) and 43.2% black (women)
Other relevant demographics: Community-dwelling sample
Anthropometrics: Baseline body composition

	Men (n=1027)	Women (n=1136)**
Body weight (kg)	81.2±12.8	70.3±14.2
Bone-free lean mass (kg)	55.2±7.1	40.0±6.0
Fat mass (kg)	23.2±6.9	28.3±9.0
Percent fat	28.2±4.9	39.5
One or more hospitalizations	439	399

**significantly different from men in all categories, P<0.05 (Student's t-test for continuous variables and chi-square test for categorical variables)

Location:
- Pittsburgh, Pennsylvania
- Memphis, Tennessee, USA.

Summary of Results:

Key Findings

Absolute changes in body composition by weight-change group in men and women¹:

	Loss ≥3% (n=692)	Stability (n=985)	Gain≥3% (n=486)
Men n	320	495	212
Men Total body weight	-5.81±3.36	-0.05±1.37	4.79±2.36
Men Total body bone-free lean mass²	-3.27±2.05	-0.93±1.41	1.07±1.74
Men Total fat mass²	-2.46±2.42	0.93±1.55	3.76±2.34
Women n	372	490	274
Women Total body weight²	-5.88±4.26	-0.07±1.21	4.59±2.62
Women Total body bone-free lean mass²	-2.09±1.78³	-0.30±1.16³	1.16±1.44
Women Total fat mass²	-3.72±3.40³	0.27±1.36³	3.45±2.28

¹A significant interaction between the direction of the weight change and sex for changes in total body bone-free lean mass (ANCOVA, P<0.0001) therefore the results are presented by sex

²Significantly different by weight-change group, P<0.05 (one-way ANOVA). All pairwise comparisons between the three weight-change categories were significantly different, P<0.0167 (t-tests with Bonferroni adjustment)

³Significantly different from men within each weight-change group, P<0.05 (Student's t-test)

Weight loss of ≥3% occurred in 31.2% of men and 32.8% of women and weight gain of ≥3% occurred in 20.6% of men and 24.1% of women (P<0.05). The remainder of the subjects maintained their weight within 3% of baseline.
Mean absolute loss of total body weight did not differ between men and women, but the absolute loss of lean mass was significantly (P<0.05) greater in men than in women
In both men and women, significantly less lean mass was gained in the weight-gain group than was lost in the weight loss group
Changes in body composition were significantly, but not strongly, associated with initial body composition in both men and women. Weight lost by men had a composition of 60.2% lean mass, whereas men had an initial composition of 68.4% lean (r=0.23, P<0.0001). Weight lost by women had a composition of 39.5% lean, whereas baseline weight composition was 57.3% lean (r=0.18, P<0.0005). In weight gainers, a smaller proportion of weight that was gained was lean (21.4% in men and 24.3% in women). No correlation was seen in men, but the correlation (r= -0.25, P<0.0001) was stronger in women.
In men, a significant interaction was observed between weight loss and hospitalization for the loss of lean mass (β±SE kg lean loss with weight loss: 0.438±0.029 in hospitalized men and 0.325±0.042 in non-hospitalized subjects). No significant interaction was noted in women after adjustment for other factors.

Author Conclusion:

With weight change, a greater proportion of lean mass than of fat mass was conserved
Significantly more lean mass was lost with weight loss than was gained with weight gain, especially in older men
Weight loss, even with weight regain, could accelerate sarcopenia in older adults
In weight-stable individuals, a pattern of lean mass loss and fat mass gain was observed, but the magnitude of this change was fairly small compared with the large loss of lean mass that accompanies weight loss.

Funding Source:

Government:

National Institute on Aging

Reviewer Comments:

Results applicable to community-dwelling older adults and can not be generalized to institutionalized individuals
Follow-up rate was 70.3% of the original cohort. Reasons for withdraw included death, failure to contact or inability to complete follow-up analysis. Excluded participants were more likely to be black, and current smokers and less likely to be high school graduates.
The cohort studied was fairly healthy and well-functioning at baseline
While BMI was not reported, mean weights at baseline seem to indicate that this cohort was made up of healthy and slightly overweight individuals. Results may not be generalized to obese or extremely thin older adults.
Weight and body composition was measured twice, at baseline and four-year follow-up. The possibility that subjects could have undergone one or more weight cycles during the course of the study was not investigated.
Reasons for weight loss or gain were not 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?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	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?	Yes
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.)	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?		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?	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