EAL

GDM: Calorie Level (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To assess how well-nourished women meet the energy demands of pregnancy and to identify factors that predict an individual's metabolic response.

Inclusion Criteria:

Healthy
Nonsmoker
Planning a pregnancy

Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Recruitment

Recruitment methods not specified.

Design: Cohort Study

Blinding Used (if applicable): not applicable

Intervention (if applicable):

Resting metabolic rate, diet-induced thermogenesis, total energy expenditure, activity energy expenditure, energy intake and body fat mass measured longitudinally.

Statistical Analysis

Longitudinal data were analyzed by univariate repeated measures ANOVA. If significant effects were observed, Tukey's Studentized range test at a procedure-wise error rate of 5% was used to determine which stage of pregnancy significantly affected the variables measured. Multivariate regression analyses were done to determine the individual contribution of each predictor variable to the outcomes variables.

Data Collection Summary:

Timing of Measurements

Studies were done in a metabolic ward and testing was done after a 10-hr fast.
5 study periods: before pregnancy (t₀), at 8-10, 24-26, and 34-36 wk gestation (t₁, t₂ and t₃, respectively) and 4-6 wks postpartum (t _post).

Dependent Variables

resting metabolic rate (RMR) was done after a 10-hr fast for 30 minutes using a metabolic cart.
diet induced thermogenesis (DIT) was measured after eating a breakfast meal containing 750 kcal (75% carbohydrate, 10% protein, 15% fat).
total energy expenditure (TEE) was determined using doubly labeled water method.
activity energy expenditure (AEE) was calculated as the difference between TEE and RMR.
energy intake (EI) was determined using 3-d weighed food records during each study period.
body fat mass (FM) was measured by densitometry.

Independent Variables

Stage of pregnancy

Control Variables

Description of Actual Data Sample:

Initial N: 16 women recruited

Attrition (final N): 10 completed the study

Age: mean age 29.1 +/- 5.0 years

Ethnicity: not mentioned

Other relevant demographics:

Anthropometrics:

Location: San Francisco Bay area, California

Summary of Results:

Other Findings:

Resting metabolic rate:

The average in RMR by t₃ was 377 kcal (range: 110 to 810 kcal) or 29% above the average t₀ value.

Diet induced thermogenesis:

The average DIT response to breakfast was 7.2% of the energy content of the meal at t₀; this ¯ to 5.7% by t₃ however there was a great deal of variation between subjects (range: -64 kcal to +26 kcal).

Total energy expenditure:

The average in TEE by t₃ was 523 kcal (range: -25 kcal to +818 kcal) or 24% higher than the average value at t₀. The average t_pos_t value was not significantly different than t₀.

Energy for activity:

AEE on average by 146 kcal by t₃ or 23% higher than the mean t₀ value (range: -550 kcal to +700 kcal).

Energy intake:

The average energy intake increased by 9% or 185 kcal /d above t₀ by t₃.

(range: -62 kcal to +520 kcal).

Fat mass:

The mean for fat deposition by t₃ was 4.5 kg (range: -0.6 kg to +10.6 kg) and the mean amount of fat retained t_post was 2.2 kg FM compared to t₀ values.

Women with the largest cumulative increase in RMR deposited the least FM (r = -0.64, P<0.05).

Author Conclusion:

Well-nourished women use different strategies to meet the energy demands of pregnancy, including reductions in DIT or AEE, increases in EI, and deposition of less FM than anticipated. The combination of strategies used by individual women is not wholly predictable from prepregnant indexes. The use

Of a single recommendation for increased energy intake in all pregnant women is not justified.

Funding Source:

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

The mean gestational weight gain was 11.6 + 4.3 kg for women with a mean prepregnancy BMI of 23.1 + 2.1. The mean birth weight of the infants was 3.55 kg (2.70 to 4.45 kg). Thus, the best indicator of adequate kcal intake is weight gain during pregnancy.

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?	N/A
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?		N/A
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	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?	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.)	N/A
	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?		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?	N/A
	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?	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