EAL

NAP: Training (2014)

Citation:

Cocate P, Pereira L, Marins J, Cecon P, Bressan J, AlfenasR. Metabolic responses to high glycemic index and low glycemic index meals: A controlled crossover trial. Nutr J. 2011; 10: 1-10.

Study Design:

Randomized Crossover Trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To investigate the effect of consuming two daily high glycemic index (HGI) or low glycemic index (LGI) meals for five consecutive days on substrate oxidation before the exercise and in the concentrations of glucose, insulin and free fatty acids before and during a high-intensity exercise.

Inclusion Criteria:

Male cyclists
Normal blood pressure
Dietary restrain scores of 14 or less based on restraint scale
Accustomed to routine, vigorous exercise at least three times per week.

Exclusion Criteria:

Female
Alcohol consumption
Smoking tobacco
Use of any medication
Following therapeutic diet
Dietary restrain score higher than 15.

Description of Study Protocol:

Recruitment

Public advertisement.

Design

Randomized crossover trial: Two five-day experimental sessions in which subjects were randomly assigned to consume either HGI or LGI meals for breakfast and lunch at the laboratory. Two sessions were separated by a washout period of at least one week.

Intervention

HGI or LGI meals.

Test Meal

Type of Sugar Added To the Meal

(g)

Weight

(g)*

Energy Density

(Kcal per g)

CHO

(Percent Total Kcal)

PRO

(Percent Total Kcal)

Fat

(Percent Total Kcal)

Fiber

(g per 100g)

HGI

Glucose 44.66±2.24

468±53.24

1.4

83.5

7.2

9.4

10.5

LGI

Fructose 21.3±1.83

646.24±72.23

1.1

83.5

7.2

9.4

10.5

*The weight of the test meals (mean ±SD) varied according to the body weight of the subjects.

Statistical Analysis

A three-way ANOVA was used to analyze differences in the physiological and metabolic responses in both study sessions
A two-way ANOVA was also used to evaluate the differences in the area under the curve (AUC) in the experimental sessions
SPSS=10.0.5
P<0.05.

Data Collection Summary:

Timing of Measurements

First and last days of study session:
- BMI
- Body fat percentage
- Respiratory exchange ratio
- Diet-induced thermogenesis
- Substrate oxidation rate.
Zero, 30, 60, 90, 120, 130, 140 and 150 minutes after test meal consumption:
- Glucose
- Insulin
- Fatty acid levels.
Immediately before exercise and 10, 20 and 30 minutes during exercise: Blood lactate.

Dependent Variables

Glycemic response: Blood sample, mg per dL
Insulinemic response: Blood sample
Lactate concentration
Free fatty acid concentration
Substrate oxidation rate
Respiratory quotient.

Independent Variables

HGI meal: Cornflakes, whole milk (glucose added), sports drink, white bread and margarine
LGI meal: All Bran cereal, fat-free strawberry yogurt, grape juice (fructose added), multi-grain bread, margarine and apple.

Control Variables

There were no significant differences between macronutrient composition, fiber content or energy density between the LGI and HGI meals
Subjects were instructed to consume meals within 15 minutes
Test meals contained one-third total energy of each participant's resting metabolic rate and contained approximately 2g of available carbohydrate per kg body weight
GI content of dinner: Study participants were counseled to have GI foods at dinner similar to that of their breakfast and lunch
Subjects were asked to maintain a constant level of physical activity during the study.

Description of Actual Data Sample:

Initial N: 15 males
Age: 24.4±3.8 years.

Other relevant demographics

VO_{2 MAX}: 70.0±5.3ml per kg^-1 per minute^-1.

Anthropometrics

BMI: 21.9 ± 1.4 kg/m²
Percent BF: 7.7±2.5%

Location

Brazil.

Summary of Results:

Key Findings

Peak glycemic and insulinemic responses (IR) were reached 30 minutes after the consumption of the test meals. These responses were significantly higher in the HGI meals than in the LGI meals on Days One and Five.

Other Findings

There was no statistical difference between heart rate, blood pressure and perceived exertion between subjects in the two study sessions
There were no differences in lactate or free fatty acid concentrations between the study treatments
The concentration of FFAs at baseline was significantly higher than that at 110 minutes after ingestion of the HGI meal on Day Five
Fasting fat and CHO oxidation rates were similar in both experimental sessions
The study treatment did not affect the respiratory exchange ratio evaluated in the fasting state or during DIT evaluation
The respiratory exchange ratio with fasting was lower than that during the DIT assessment of both days of the HGI and LGI sessions. There were significantly higher DITs on Days One and Five of the LGI session than on the same days of the HGI session.

Author Conclusion:

The consumption of a HGI meal resulted in greater areas under the glycemic and the insulinemic curves than the ingestion of an LGI meal did on Days One and Five. However, there were no differenced in the glycemic and insulinemic responses during exercise, nor were concentrations of lactate or free fatty acids affected. The HGI meal led to higher fat oxidation while the LGI meal lead to higher CHO oxidation. Post-prandial energy expenditure was not affected by HI of the ingested meal.

Funding Source:

Government:

(Brazilian) FAPEMIG

Reviewer Comments:

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?		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?	Yes
	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?	No
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?		???
	4.1.	Were follow-up methods described and the same for all groups?	???
	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%.)	???
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	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?	???
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.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	No
	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?	No
	6.6.	Were extra or unplanned treatments described?	No
	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?	No
	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?		???
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	No
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