EAL

NAP: Training (2007)

Citation:

Stepto NK, Carey AL, Staudacher HM, Cummings NK, Burke LM, Hawley JA. Effect of short-term fat adaptation on high-intensity training. Med Sci Sports Exerc. 2002; 34 (3): 449-455.

PubMed ID: 11880809

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 determine whether competitive endurance athletes could complete high-intensity training sessions, typical of those that are incorporated into a taper, while consuming a high-fat diet.

Inclusion Criteria:

History of over four years of regular endurance training (20±6 hours per week)
Either national- or international-level athletes, all highly-trained competitive ultra-endurance athletes.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: Subjects were recruited, but methods not described
Design: Randomized crossover trial
Blinding used: Impossible to blind the diets, but investigators were blinded for data collection
Intervention: Subjects consumed either three days of high-carbohydrate or high-fat diet
Statistical analysis: Data analyzed using repeated-measures three-way ANOVA (diet x day x time). The volume of training and RPE during training sessions on the two different diets were analyzed with paired T-tests.

Data Collection Summary:

Timing of Measurements

Subjects consumed three days of either high-carbohydrate or high-fat diet, separated by 18-day washout period
On the first and fourth days of each treatment, subjects completed a standardized laboratory training session consisting of a 20-minute warmup at 65% VO_2peak immediately followed by eight five-minute work bouts at 86±2% of VO_2peak with a 60-second recovery.

Dependent Variables

Continuous blood sampling analyzed for glucose and lactate concentrations
Plasma glycerol concentration measured by enzymatic fluorometric analysis
Heart rates monitored via telemetry
Subjective ratings of perceived exertion for the legs
Profile of Moods State
Rates of substrate oxidation calculated by gas analysis measurements during indirect calorimetry.

Independent Variables

Isoenergetic diets: High-fat; low-CHO diet (over 65% fat, less than 20% CHO); high-carbohydrate; low-fat (70%-75% CHO, under 15% fat)
All meals and snacks supplied to subjects, one supervised meal in lab each day
Subjects kept food diary and daily training records.

Description of Actual Data Sample:

Initial N: Seven athletes, all male
Attrition (final N): Seven
Age: Mean, 24±6 years
Ethnicity: Not mentioned

Other Relevant Demographics

Mean weight: 75.3±5.8kg
Mean VO_2max: 5.0±0.5L per minute.

Location

Australia.

Summary of Results:

	High-CHO; Day One	High-CHO; Day Four	High-Fat; Day One	High-Fat; Day Four
VO₂; SS ride	3.19±0.22	3.18±0.27	3.21±0.24	3.27±0.22
VO₂; Work Bout One	4.25±0.40	4.26±0.40	4.25±0.36	4.33±0.36
VO₂; Work Bout Four	4.32±0.42	4.26±0.37	4.32±0.40	4.38±0.30
VO₂; Work Bout Eight	4.35±0.39	4.32±0.32	4.40±0.33	4.53±0.23
RER; SS ride	0.85±0.03	0.85±0.03	0.85±0.04	0.79±0.03
RER; Work Bout One	0.94±0.04	0.94±0.03	0.94±0.05	0.86±0.03
RER; Work Bout Four	0.92±0.03	0.91±0.03	0.90±0.03	0.85±0.03
RER; Work Bout Eight	0.91±0.03	0.90±0.04	0.90±0.03	0.85±0.02

Other Findings

Subjects had excellent dietary compliance and fat and CHO intakes were significantly different (P<0.001). CHO intakes were 11.00±0.03 and 2.60±0.07g per kg per day and fat intakes were 1.01±0.03g per kg per day and 4.62±0.23g per kg per day on the high-CHO and high-fat diets.
Respiratory exchange ratio (mean for Bouts One, Four and Eight) was similar on Day One for the high-fat and high-carbohydrate diets (0.91±0.04 vs. 0.92±0.03) and on Day Four after the high-carbohydrate diet (0.92±0.03), but fell to 0.85±0.03 on Day Four after the high-fat diet (P<0.05)
Blood lactate concentration was similar on Days One and Four of the high-carbohydrate diet (3.5±0.9 and 3.2±1.0) and on Day One of the high-fat diet (3.7±1.2mM) but declined to 2.4±0.5mM on Day Four after the high-fat diet (P<0.05)
Ratings of perception of effort were similar on Day One for high-fat and high-carbohydrate (14.8±1.5 vs. 14.1±1.4) and on Day Four after the high-carbohydrate diet (13.8±1.8) but increased to 16.0±1.3 on Day Four after the high-fat diet (P<0.05)
The POMS score for fatigue was similar (42±21 vs. 35±20) for the high-CHO and high-fat diets on Day One, but was higher on the day of high-fat (66±18, P<0.01).

Author Conclusion:

Competitive endurance athletes can perform intense interval training during three-day exposure to a high-fat diet, and such exercise elicits high rates of fat oxidation, but compared with a high-carbohydrate diet, training sessions were associated with increased ratings of perceived exertion.

Funding Source:

Industry:

Nestle Australia

Food Company:

Reviewer Comments:

Recruitment methods not described, but only ultra-endurance athletes were studied
Food provided to subjects.

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?		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?	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?	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)?	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?	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