EAL

NAP: Training (2007)

Citation:

Fleming J, Sharman MJ, Avery NG, Love DM, Gomez AL, Scheett TP, Kraemer WJ, Volek JS. Endurance capacity and high-intensity exercise performance responses to a high-fat diet. Int J Sport Nutr Exerc Metab. 2003; 13 (4): 466-478. PubMed ID: 14967870

Study Design:

Randomized controlled trial

Class:

A - Click here for explanation of classification scheme.

Quality Rating:

POSITIVE: See Quality Criteria Checklist below.

Research Purpose:

To examine the effects of a six-week high-fat moderate-protein diet on maximal oxygen consumption, power output during high-intensity exercise and prolonged endurance exercise.

Inclusion Criteria:

Subjects between the ages of 19 and 56, recreationally active, habitually consuming greater than 45% carbohydrate in their diet (assessed via seven-day food records), with no medical problems, non-smoking and with no goals of weight loss.

Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Recruitment: Methods not defined
Design: Randomized controlled trial
Blinding used: Not used
Intervention: Assigned to either a high-fat moderate-protein or control group for six weeks.

Statistical Analysis

Data analyzed using two-way ANOVA with group and time as main effects
When a significant main effect or interaction effect was detected, a Fisher's LSD test was used to locate the pairwise differences between means
The level of significance was set at P<0.05.

Data Collection Summary:

Timing of Measurements

Measurements made before and after six weeks of diet and training.

Dependent Variables

Maximal oxygen consumption test and gas collection analysis
Two 30-second Wingate anaerobic test sprints
45-minute timed ride
Training logged during the six-week period
Body composition through DEXA.

Independent Variables

High-fat moderate-protein diet (60% fat) or control diet (25% fat)
Portion of foods were provided to subjects through weekly meetings with dietitian to review compliance
Subjects given appropriate foods, recipes, sample meal plans, food measuring utensils, scales
Subjects kept food records every day in high-fat moderate-protein group and only Weeks One and Six in control group
Given standard pre-exercise meals prior to all exercise tests: 361kcal (53% protein, 10% carbohydrate, 37% fat) prior to maximal oxygen consumption test; 221kcal (40% protein, 5% carbohydrate, 55% fat) prior to Wingate anaerobic tests.

Description of Actual Data Sample:

Initial N: 20 men; 12 in high-fat moderate-protein and eight in the control group
Attrition (final N): 20 men.

Age

High-fat/moderate protein, mean: 36±12 years
Controls, mean: 35±13 years.

Ethnicity

Not mentioned.

Other Relevant Demographics

High-fat moderate protein VO_2max: 44.2±2.0ml per kg per minute
Controls VO_2max: 46.2±3.8ml per kg per minute.

Anthropometrics

There were no significant differences between groups in baseline variables.

Location

Connecticut.

Summary of Results:

	High-Fat Baseline	High-Fat Week Six	Control Baseline	Control Week Six
Energy (Kcal)	2,540±590	2,335±375	2,029±469	1,815±195
Protein (Percentage)	113±40	176±45	82±16	70±10
CHO (Percentage)	17±4	30±5	16±2	15±1
Fat (Percentage)	306±100	46±10	287±79	271±47
VO_2max (ml per kg per minute)	44.2±2.0	42.8±1.1	45.5±3.3	45.2±3.6
VO_2max (L per minute)	3.50±0.1	3.27±0.1	3.84±0.2	3.82±1.6
Max HR (BPM)	187±3.5	181±3.5	178±3	175±3
RER	1.19±0.02	1.13±0.02	1.14±0.01	1.14±0.01

Other Findings

Body mass decreased significantly (-2.2kg, P<0.05) in the high-fat moderate-protein subjects, while control subjects gained an average of 0.1kg
Maximal oxygen consumption significantly decreased in the high fat moderate protein group (3.5±0.14 to 3.27±0.09L per minute), but was unaffected when corrected for body mass
Perceived exertion was significantly higher during this test in the high-fat moderate-protein group
Main time effects indicated that peak and mean power decreased significantly during Bout One of the Wingate sprints in the high-fat moderate-protein group (-10% and -20%, respectively), but not the control group (-8% and -16%, respectively). No change was noted between groups during Bout Two.
Only peak power was lower during Bout One in the high-fat moderate-protein group when corrected for body mass
Despite significantly reduced respiratory exchange ratio values in the high-fat moderate-protein group during the 45-minute cycling bout, work output was significantly decreased (-18%).

Author Conclusion:

Adaptation to a six-week high-fat moderate-protein diet in non-highly trained men resulted in increased fat oxidation during exercise and small decrements in peak power output and endurance performance
Although this study did not attempt to establish the mechanisms for these performance effects, the deleterious effects on exercise performance may be accounted for in part by a reduction in body mass or increased ratings of perceived exertion.

Funding Source:

University/Hospital:

University of Connecticut

Reviewer Comments:

Compliance checked through dietitian interview
Diet length of six weeks shows long-term effects.

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?	Yes
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)	???
	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?		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?	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?	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?	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?	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