Gestational Diabetes and Physical Activity

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

To test whether a single exercise session reduces fasting glycemia and insulin concentration and glycemic and insulin excursion following a mixed nutrient meal in women with gestational diabetes secondary to a postexertional increase in insulin sensitivity.

 

 

Inclusion Criteria:

1.  28 to 38 wks gestation

2.  free of medical or obstetrical problems other than GDM

3.  did not engage in any form of regular physical activity

Exclusion Criteria:
Not described.
Description of Study Protocol:

Recruitment:  Subjects were recruited from the outpatient department at Women and Infants Hospital of Rhode Island and private physicians' offices

Design: Randomized Crossover Trial

Blinding Used (if applicable): Not described.

Intervention (if applicable):

  • Computer-generated random numbers were used to determine the order with which each subject would complete the two protocols. 
  • The two protocols were identical with the exception of an exercise sesssion 14 h before one of the meals.  Each subject completed the alternate protocol one week later.
  • Subjects followed 2,200 kcal diet, for 3 days prior to the study.
  • Exercise 14 hours prior to meal: 30 minutes on stationary bicycle at 60% VO2max
  • Continuous monitoring of maternal heartrate
  • Fetal heart rate measured before and after exercise session
  • Study meal contained 600 kcal, 50% carbohydrate, 20% protein, 30% fat
  • Blood glucose and insulin levels after meal drawn at :  1, 10, 30, 60, 90, 120, 150, 180min

Statitistical Analysis:  Student paired t-test and correlation analysis

Data Collection Summary:

Timing of Measurements: Subjects were 28-38 weeks EGA, for timing of specific interventions see description above.

Dependent Variables:

  •         Fasting glucose and insulin levels
  •         Peak glucose and insulin levels
  •         Incremental area of the glycemic and insulin curves

Independent Variables: 

  • Exercise session

Control Variables:  No control variables used.  Crossover design used. 

Description of Actual Data Sample:

Initial N:  11, 6 GDM and 5 controls

Attrition (Final N): 11

Age:  GDM = 27.6 + 2.8, nonGDM = 23.7 + 2.0

Ethnicity:  Not described.

Other Relevant Demographics:  Not described.

Anthropometrics: 

  Non GDM GDM P
BMI (prepreg) 24.3 + .9 25.9 + 1.8 .46
BMI (preg) 29.1 + 1.3 31.8 + 1.9 .29
Wt Change during preg kg 12.0 + 3.0 14.4 + 1.5 .48

Location: Rhode Island

Summary of Results:

Other Findings

There were no differences in fasting glucose or insulin levels, peak glucose or insulin levels or areas under the glucose and insulin curves were detetected for those with gestational diabetes or normal pregnant women or between the two groups of women.

The relationship between fasting insulin levels and the change in I/G ration between the control and exercise protocols was examined to determinewhetehr exercise might improve insulin sensitivity in a subset of patients who are considered insulin resistant.  As expected, subjects with lower fasting insulin levels in the control trial had lower I/G ratios (r=.98;P<.01), and thus exhibited greater insulin sensitvity than subjects with hihger fastin ginsulin levels.   The relationship between fasting insulin levels and the change in I/G ratio was not significant.

 

 

 

Author Conclusion:

Results from this study indicate a single bout of exercise did not blunt the glycemic response observed following a mixed nutrient meal.  In addition, the total insulin response to the meal was similar regardless of whether it was preceded by a bout of exercise.

We conclude that in a “real-life” situation, a moderate bout of exercise in the evening is unlikely to improve the glycemic or insulin response to a meal-breakfast the following morning.  While exercise appears to be an attractive option for patients with gestational diabetes, and most likely does not cause any harm, the beneficial effects of acute exercise on maternal metabolism remains to be identified.  The effect, if any, of exercise in improving glycemia in women with gestational diabetes, may be secondary to the chronicity of training rather than a sum of the individidual events.

Funding Source:
University/Hospital: Brown University School of Medicine, University of Arizona Health Science Center
Reviewer Comments:

Small sample size.  

Descriptive statistics not reported.

The authors suggest that it may not be feasible to see effects in a single session; results from multiple session would be interesting to see.

No intake data reported such that we don't know if each participant ate the whole meal.

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? 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.) 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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  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? 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? 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? ???
  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)? N/A
  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? Yes
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? ???
  10.2. Was the study free from apparent conflict of interest? ???