EAL

GDM: Weight Management (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To better understand the metabolic consequences of marked calorie restriction in obese pregnant women with gestational diabetes.

Inclusion Criteria:

Obese: >120% of IBW as defined by the corrected 1959 Metropolitan Life Insurance tables.
Gestational diabetes: All women were screened with a 50 g 1-hr glucose challenge; those with plasma glucose >7.8 mmol received the 3-hr 100 gm glucose challenge.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

Obese women diagnosed with gestational diabetes at the University of Washington. Subjects were hospitalized during study.

Design: Randomized Controlled Trial.

Blinding Used (if applicable): not used

Intervention (if applicable):

OB clinics were randomly assigned to a 2400 kcal or 1200 kcal diet.

Wk 1: 2400 kcal diet: breakfast 8 a.m. 25% kcal, 12 noon lunch: 25% kcal, 3 p.m. snack: 12.5% kcal, 800 dinner: 25% kcal, 10 p.m. snack: 12.5% kcal
Wk 2: ½ of subjects randomly assigned to 1200 kcal diet, same distribution of kcal as 2400 kcal diet.

Statistical Analysis

Wilcoxon rank-sum test to determine differences between groups. Authors note that power to detect significant differences may be limited.

Data Collection Summary:

Timing of Measurements

Diets were followed for 2 weeks, measurements made at baseline and at end of each dietary period.

Dependent Variables

Fasting blood glucose; 3-hr OGTT curve
Fasting plasma insulin
Fasting TG, free fatty acids, glycerol, beta-hydroxybutyrate
Urinary ketones

Independent Variables

2400 kcal or 1200 kcal diet

Control Variables

Description of Actual Data Sample:

Initial N: 12 subjects participated in the study. 5 served as controls on 2400 kcal and 7 experimental on 1200 kcal the 2^nd wk of the study.

Attrition (final N): 12 subjects

Age: mean age controls: 36 +/- 5 years, calorie-restricted: 30 +/- 4 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics: The study groups were similar in terms of age, prepregnancy weight, prepregnancy percent of IBW, number of prior pregnancies, and duration of current pregnancy at study initiation.

Location: Seattle, WA

Summary of Results:

Other Findings:

24-hr mean glucose levels did not change in the control group but decreased significantly in the calorie restricted group (wk 1: 6.7+1.0 mmol vs. wk 2: 5.4+0.5 mmol) (P<0.01).

Fasting plasma insulin decreased significantly in the calorie restricted group (265+165 pmol wk 1 vs. 145+130 pmol wk 2) (P<0.02)

Fasting beta-hydroxybutyrate increased in the calorie restricted group (290+240 mmol wk 1 vs 780+30 mmol wk 2) but not in the control group (P<0.02).

Urine ketones increased significantly in the calorie restricted group (P<0.02).

Author Conclusion:

Consuming a diet with 1200 kcal/d improves glycemic status in obese pregnant women with gestational diabetes but causes significant increases in ketonemia and ketonuria. Because of the impact of ketonemia and ketonuria on fetal well-being is controversial, 1200 kcal restriction appears unwise for general clinical usage.

Funding Source:

University/Hospital:

University of Washington

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

Well controlled study but small sample size. Did not report distribution of carbohydrates, only kcal. Experimental subjects were more obese than controls.

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)	???
	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?		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?	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?	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?		???
	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?	???
	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?	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?	???
	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?	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