EAL

NAP: Training (2014)

Citation:

Stellingwerff T, Spriet LL, Watt MJ, Kimber NE, Hargreaves M, Hawley JA, Burke LM. Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration. Am J Physiol Endocrinol Metab. 2006; 290: E380-E388.

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 compare the effects of a five-day high-fat diet with one day of CHO restoration (FAT-adapt) to a six-day isoenergetic high-CHO diet (HCHO) on the regulation of key enzymes involved in skeletal muscle CHO and fat metabolism.

Inclusion Criteria:

Endurance-trained male cyclists or triathletes.

Exclusion Criteria:

Female
Non-endurance trained.

Description of Study Protocol:

Design

Randomized crossover.

Intervention

High-fat diet (4.6g per kg per day or 67% energy from fat) with low CHO (2.5g per kg per day, 18% energy) supplying 0.25MJ per kg body mass (BM) and 2.3g per kg protein (15% energy). Control (HCHO) was a protein and energy-matched diet providing 10.3g per kg per day and 70% of energy from CHO and 1.0g per kg and 15% energy from fat. Fiber was kept to a daily mean intake of approximately 40g. All food was supplied and food diaries were checked for compliance.

Statistical Analysis

Two-way repeated measures ANOVA (treatment x time) was used to determine significant differences between treatments during the steady-state 70% V_02peak cycling portion. When a significant F-ratio was obtained, post-hoc analysis was completed using a Student-Newman-Keals test. All post-sprint and post-TT blood and muscle measurements, glycogen utilization and TT performance and any net calculated differences between selected time points between the FAT-adapt and HCHO trials were compared using a paired dependent-samples T-test.

Data Collection Summary:

Timing of Measurements

Muscle biopsies on day seven at rest, after one minute of SS cycling, immediately after 20 minutes of SS cycling, and immediately after a 60-second all-out sprint. Blood tests are done on day seven at baseline, five minutes and 20 minutes during SS cycling, after a 60-second sprint and after TT. Pulmonary gas collection at 15 minutes to 20 minutes of SS cycling.

Dependent Variables

Respiratory exchange ratio: Gas system analyzer
Muscle HSL and PDH activity, creatine (Cr), phosphocreatine (PCr), ATP, lactate, glucose-6-phosphate (G-6-P), acetyl-CoA, acetylcarnitine, pyruvate, glycogen: Muscle biopsy of vastus lateralis muscle of leg
Free ADP and AMP, free inorganic phosphate, substrate level phosphorylation and total glycogenolysis: Calculated from muscle metabolites
CHO and fat oxidation: Calculated from respiratory data
Lactate, glucose, insulin, FFA, epinephrine, norepinephrine: Blood via catheter in antecubital vein.

Independent Variables

HCHO or FAT-adapt diet for days one to five, HCHO diet on day on six.

Control Variables

Training sessions of long slow distance (LSD), LSD with hills, interval training and LSD respectively on days one to five of both trials
The subjects rested on day six
On day seven, 20 minutes of steady-state (SS) cycling, 60-second all-out sprint at 150% PPO and a time trial (TT) of a set amount of work (4kJ per kg BM) "as fast as possible"
Familiarization of TT on day one.

Description of Actual Data Sample:

Initial N: Seven males
Attrition (final N): Seven
Age: 30.0±0.7 years.

Anthropometrics

72.7±2.9kg
VO_2peak: 60.7±2.6ml per kg per minute
Sustained PPO: 334±17W.

Location

Australia.

Summary of Results:

Findings

RER decreased (P=0.08) during the 20-minute cycle ride on FAT-adapt diet compared with HCHO diet (N=3). There was a 45% increase in fat oxidation and a concomitant 30% decrease in CHO oxidation as result of the RER shift.
No difference in blood lactate, glucose, insulin, FFA, epinephrine and norepinephrine at any time point during the 20-minute ride. Plasma lactate, glucose, epinephrine and norepinephrine were increased during the 20-minute ride (P<0.05) and plasma FFA was decreased (P<0.05) by the 20-minute mark. Glucose and lactate were significantly increased after the sprint at 150% PPO and post-TT but were not different between trials.
At rest, PDHa was 56% lower following the FAT-adapt. During onset of exercise, PDHa increased rapidly and similarly in both trials but continued to be 29% lower throughout the 7% VO_2peak cycling during FAT-adapt compared with HCHO (P=0.003). After a one-minute rest and subsequent one-minute sprint PDHa increased rapidly and similarly in both trials but remained lower (P≤0.05) in FAT-adapt. Increase in PDH activation during the one-minute sprint was not different between diets.
HSL activity was 30% higher after the five-day high-fat diet with CHO restoration compared with HCHO but did not reach significance. Increase in HSL activity at onset of exercise was not different between trials, such that HSL activity remained 20% higher (P=0.12) after the FAT-adapt vs HCHO. HSL rapidly decreased (P≤0.05) during the one-minute 150% PPO sprint and there was no difference between diets.
There was no difference between diets in PCr, muscle content of ATP, ADPr, AMPf during rest and 20 minutes of cycling. ADPr and AMPf were greater (P≤0.05) after a one-minute PPO sprint during HCHO vs. FAT-adapt. P_1fincreased (P≤0.05) similarly during exercise for both diets
There was no difference in pre-experimental trial glycogen contents following one day of CHO restoration between dietary treatments. Resting muscle G-6-P and glucose content were similar and increased to the same extent during SS. There was a significantly higher G-6-P content post-sprint after HCHO. Pyruvate and lactate contents were not different at rest, during exercise at 70% VO_2peak, and after a 150% PPO sprint. The net differences in accumulations of G-6-P, pyruvate and lactate, coupled with PDHa differences during the first minute of exercise at 70% VO_2peakresulted in a higher
(P≤0.05) estimated glycogenolysis in HCHO vs. FAT-adapt. Estimated glycogenolysis remained higher in HCHO during a one-minute sprint.
Acetyl-CoA and acetylcarnitine were similar at rest and at one-minute SS and both diets had parallel increases (P≤0.05) after 20 minutes of submaximal exercise and one-minute sprint
During the first minute of exercise at 70% VO_2peak substrate phosphorylation was decreased by 49% exercise at 70% VO_2peak (P<0.05) following FAT-adapt vs. HCHO. This trend continued during a one-minute sprint at 150% PPO, as FAT-adapt resulted in a 22% decrease in estimated substrate phosphorylation compared with HCHO.
There was no difference between-treatment differences in time to complete the 4kJ per kg BM TT, mean power output or the percent (PPO) sustained throughout the TT.

Author Conclusion:

Previously reported decreases in whole body CHO oxidation and increases in fat oxidation after the FAT-adapt protocol are a function of metabolic changes within skeletal muscle.

Funding Source:

University/Hospital:

Deakin University, Australian Institute of Sport

Not-for-profit

Natural Sciences and Engineering Research Council, Canada

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?		N/A
	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)	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?		N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	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?		N/A
	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?	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?	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?	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?	N/A
	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