EAL

AWM: Low Glycemic Diets (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate the impact of adding education of the glycemic index of foods to a behavioral weight loss program.

Inclusion Criteria:

Included if obese (BMI > 30), sedentary, nonsmokers, and cleared for participation by physician.

Exclusion Criteria:

Excluded if they had cardiovascular disease, musculoskeletal problems, IDDM or uncontrolled type 2 diabetes, and elevated resting blood pressure (>160/100 mm Hg).

Description of Study Protocol:

Recruitment

Recruited through local advertisements.

Design

Randomized Controlled Trial.

Blinding used (if applicable)

Not used.

Intervention (if applicable)

Subjects randomized to receive either a behavioral weight loss program with or without glycemic index education.

Statistical Analysis

Baseline differences between treatment groups assessed using ANOVA and chi-square tests. Pre- and post-treatment effects were evaluated using 2-way repeated measures ANOVA with treatment groups as the between group factor. Weight loss, body composition and diet were used as dependent measures. One year post-treatment effects also examined using repeated measures ANOVA.

Data Collection Summary:

Timing of Measurements

Weight loss, body fat and diet assessed at baseline, after 20 weeks of treatment and after 1 year.

Dependent Variables

Body weight obtained with digital scale
Body fat obtained with leg-to-leg bioelectrical impedance
Dietary assessment based on 4-day food records. Average daily glycemic index and glycemic load determined from published tables.
Glycemic index knowledge determined from questionnaire (a = 0.86).

Independent Variables

Behavioral weight loss program was administered in small groups over 20 weekly sessions and based on LEARN program. Education without glycemic index info lasted 60 - 75 minutes, education with glycemic info lasted 90 - 120 minutes. Glycemic index instruction focused on carbohydrate consumption and glucose and insulin levels, computing the glycemic index, physical characteristics of carbohydrates and the speed of digestion, the glycemic index and health, low glycemic index foods, hunger and satiety, and low glycemic index cooking.

Control Variables

Description of Actual Data Sample:

Initial N: 53 obese, sedentary participants, 44 women, 9 men

Attrition (final N): 40 completed the study (75.5%).

Age: Of baseline group: 43.4 +/- 9.37 years

Ethnicity: Not mentioned

Other relevant demographics: Not mentioned

Anthropometrics: Program participants not receiving glycemic index education had significantly greater baseline body fat than those receiving education [F (1,52) = 7.84, p < 0.01]

Location: Ohio

Summary of Results:

	BWLP Pre	BWLP Post	BWLP + GI Pre	BWLP + GI Post	All Pre	All Post
Weight (kg)	104.8 +/- 21.2	96.6 +/- 15.9	101.2 +/- 16.3	94.1 +/- 15.1	102.8 +/- 18.5	95.2 +/- 15.3
BMI	37.2 +/- 5.1	34.4 +/- 4.3	38.0 +/- 13.4	35.5 +/- 13.4	37.6 +/- 10.4	35.0 +/- 10.2
Body Fat (%)	45.8 +/- 3.9	41.9 +/- 5.5	42.5 +/- 4.0	38.7 +/- 6.8	44.1 +/- 4.2	40.3 +/- 6.3
GI knowledge		6.9 +/- 2.2		11.5 +/- 1.6		9.5 +/- 2.9
Calories	2272 +/- 454	1659 +/- 433	2580 +/- 607	1674 +/- 586	2443 +/- 559	1667 +/- 516

Other Findings

Participants not receiving GI education attended significantly more sessions (15.6) compared to those receiving the education (13.1) [F(1,40) = 6.79, p < 0.01].

Glycemic index education had no significant impact on body weight, BMI or body fat at posttreatment or 1 year follow-up.

Average weight loss was 7.6 kg (p < 0.01), BMI decreased by 2.6 (p < 0.01) and average body fat decreased by 8.6% (p < 0.01).

There was a significant decrease in total calories (p < 0.01).

At posttreatment, participants in the glycemic index education group had significantly greater glycemic index knowledge (P < 0.05) and consumed foods with a lower average daily glycemic index (p < 0.05) than participants without the education.

38 completed the 1 year follow-up and at 1 year posttreatment, participants regained 59% of their weight loss and 34% of their lost body fat and there was no difference between groups.

Author Conclusion:

Glycemic index education did not improve treatment outcomes in this investigation. The effectiveness of low-glycemic index diets on enhancing weight loss and long-term weight maintenance is still unclear.

Funding Source:

University/Hospital:

Bowling Green State University

Reviewer Comments:

Questionnaire tested for reliability. Dropouts not discussed. Demographics of completers not included.

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)	Yes
	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)	Yes

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?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
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)	No
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	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?	N/A
	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?		No
	4.1.	Were follow-up methods described and the same for all groups?	No
	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%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.4.	Were reasons for withdrawals similar across groups?	???
	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?	No
	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?	N/A
	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?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	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?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	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