EAL

PWM: Low Carbohydrate and Low Glycemic Index Diets (2006)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

Investigated the effect of consuming breakfasts of varying glycemic index (GI) on appetite and food intake in a group of normal weight and overweight children in grades five and six (aged nine to 11 years)
Measured food intake at lunchtime, using unobtrusive observational recordings for quantification of nutrient intake.

Inclusion Criteria:

Children in grades five and six (aged nine to 11 years)
Informed consent.

Exclusion Criteria:

Children were excluded if they:

Had a food allergy
Followed a therapeutic diet
Did not habitually eat breakfast.

Description of Study Protocol:

Recruitment

Participants were recruited from an Oxford middle school which already had a breakfast club. Special emphasis was placed on children in grades five and six (ages nine to 11 years). 38 children were recruited to the study (15 boys and 23 girls). Both nonoverweight and overweight and obese children were recruited. Children were classified as overweight and obese using BMI cutoff values, which related to the adult values of 25 and 30, respectively.

Design

Three-way randomized crossover study, in which participants acted as their own control.

Intervention (if applicable)

Participants were divided into five groups and a rolling program was devised whereby, week by week, each group would randomly receive one of three test breakfasts for three consecutive days, followed by a washout period of at least five weeks between the other test breakfasts.

The three test breakfasts were:

Low GI breakfast
Low GI with 10% added sucrose breakfast
High GI breakfast.

The test breakfasts were developed to closely match the energy and nutrient content of the participant's habitual breakfast (derived from 24-hour recall and diet history at baseline). All test breakfasts included fruit juice, cereal and milk with or without bread and margarine. Foods with an appropriate GI value were selected. The low GI plus added sucrose was similar to the low GI in macronutrient content, except for the addition of sucrose to 10% energy.
Before participants were given test breakfasts, a "trial" lunch was provided after habitual breakfast. This trial day acted as the control breakfast (habitual).
After each test breakfast, children were instructed not to eat or drink anything until lunch except water and a small serving of fruit (apple, grapes) as a midmorning snack. Lunch was served buffet-style: Children were allowed free access to a variety of foods.

Statistical Analysis

Lunch intakes were analyzed using a multilevel regression model for repeated measures. Likelihood ratio statistics to determine whether type of breakfast eaten had a signicant effect on lunch intake, controlling for sex and weight status. Friedman test for differences in palatability, satiation of breakfasts and prelunch satiety for the first, second and third experimental days. Pairwise comparisons of the three test breakfasts and between each test breakfast and habitual breakfast (mean calorie intakes plus or minus standard deviation).

Data Collection Summary:

Timing of Measurements

Anthropmetrics: Children were weighed and measured at baseline using standardized techniques. Children were classified as overweight and obese using BMI cutoff values which related to the adult values of 25 and 30, respectively.

Test breakfasts and lunch measurements: Breakfast palatability, satiation after breakfast and satiety before lunch were measured using rating scales (three test breakfasts compared separately for the first, second and third experimental days). Unobtrusive observation and recording of food selection was made using a checklist that detailed all of the foods available. Amounts consumed and plate waste were estimated. For the 37 children who completed the study, 362 records of lunch intakes and satiety ratings were made (eight missing responses).

Dietary Assessment for composition of habitual breakfasts: A 24-hour recall of dietary intake, using standardized techniques (Domel et al, 1994) and food photographs to quantify the data. In addition, a diet history of habitual breakfast consumption was obtained. Dietary assessment data were analyzed using Diet Five.

Dependent Variables

Satiety and palatability of test breakfasts
Prelunch satiety ratings
Lunch intakes after different test breakfasts.

Independent Variables

Types of test breakfast: Low GI, low GI plus added sucrose (10% energy), high GI vs. habitual breakfast.

Control Variables

Sex
Weight status (nonoverweight, overweight).

Description of Actual Data Sample:

Initial N: 38 children (15 boys and 23 girls)
Attrition (final N): 37 children completed the study (15 boys and 22 girls). One disliked the breakfasts served.
Age: Nine to 12 years (mean age 10.8±0.80 years)
Ethnicity: All Caucasian
Other relevant demographics: Mean BMI for male participants =18±1.9 (SD); mean BMI for female participants =10.9±3.9 (SD).
Anthropometrics: Made at baseline using standardized procedures. Children were classified as overweight and obese using BMI cutoff values, which related to the adult values of 25 and 30, respectively.

30% of the children were overweight or obese
70% had nonoverweight status.

Location: UK.

Summary of Results:

Satiation of Test Breakfasts

There were no significant differences between the test breakfasts in immediate satiation on first, second and third experimental days.

Palatability of Test Breakfasts

Significant differences in palatability were found on Day One and Day Two of the experimental days only (Day One, P=0.001; Day Two, P=0.000; Day Three, P=0.06).
The high GI test breakfast was rated to be more palatable than either the low GI (Day One, P=0.001; Day Two, P=0.008) or the low GI plus added sucrose test breakfasts (Day One, P=0.02; Day Two, P=0.03). However, on experimental days one and two, there were no differences in palatability between the low GI test breakfast and the low GI breakfast with added sucrose test breakfast.

Prelunch Satiety Ratings

Hunger ratings were statistically greater (a low satiety rating) after the high GI test breakfast, compared with the other two test breakfasts, for two of the three experimental days, statistically significant on Day Two (P=0.05).
Prelunch satiety scores were inversely related to subsequent food intake. For each of the lunches, a negative relationship was found, i.e., a greater hunger rating (a low satiety rating) was associated with higher energy intakes. This relationship was statistically significant on Day Three of the low GI and low GI with added sucrose breakfast (P=0.001, P=0.008) and Day Two of the high GI breakfast (P=0.001).

Other Findings

Mean lunch intakes after different breakfast types

On average, the girls ate 66 kcal less than the boys and overweight children ate 93 kcal more than their lean counterparts. However, sex and weight status did not have a significant effect on lunch intake.
Breakfast type had a significant effect on mean energy at lunch time (P<0.001). Lunch intake was lower after low GI and low GI plus added sucrose, compared with lunch intake after high GI and also habitual breakfast (high GI; mean habitual breakfast intake obtained from a 24-hour recall and diet histories) (P<0.001). 17% of the intraindividual variation in children in lunchtime intake was explained by the type of breakfast eaten.
Pairwise comparisons of lunchtime kcal were as follows (mean±SD):

High GI > low GI = 145±47 kcal
High GI > low GI with added sucrose = 119±53 kcal
Low GI plus sucrose > low GI =27±54 kcal
Low GI < habitual = -109±74 kcal
Low GI plus added sucrose < habitual = -83±75 kcal
High GI > habitual = 36±75 kcal.

Author Conclusion:

"The results suggested that low GI foods eaten at breakfast have a significant impact on food intake at lunch. There was a significantly lower mean lunch intake after the low GI breakfasts (low GI and low GI plus added sucrose), compared with mean lunch intake after the high GI and habitual breakfasts. In addition, on two of three experimental days, mean hunger ratings were greater (i.e., satiety ratings were lower) after the high GI breakfast, compared with the other two test breakfasts."
Results of this study were similar to other studies that found an increase in satiety or a decrease in food intake after the consumption of low GI foods.

Funding Source:

Industry:

Sugar Bureau

Commodity Group:

University/Hospital:

Oxford Brooks University

Reviewer Comments:

Limitations

Failure to match macronutrient (carbohydrate, protein, fat) of the three test breakfasts' content to reduce possibility of confounding variables
Failure to match dietary fiber content of the test breakfasts
Limited generalizability (other age groups, other ethnic groups).

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)	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?	N/A
	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?	N/A
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)	Yes
	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.)	No
	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?	N/A
	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?		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?	???
	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?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	Yes
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?	???
	7.7.	Were the measurements conducted consistently across groups?	N/A
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?	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?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	???