Comparing Acute, High Dietary Protein and Carbohydrate Intake on Transcriptional Biomarkers, Fuel Utilisation and Exercise Performance in Trained Male Runners.
Study Goal
The researchers aimed to determine the impact of a short-term high-protein, reduced-carbohydrate diet on endurance performance and gene markers of training adaptation in trained runners.
Results Summary
The high-protein diet significantly reduced high-intensity exercise performance (23.3% decrease in time to exhaustion) and increased fat oxidation during submaximal exercise, but these effects reverted upon returning to a habitual diet. The high-carbohydrate diet improved time to exhaustion (6.5% increase) and modestly increased gene markers of adaptation.
Population
16 trained endurance runners (maximal oxygen uptake: 64.2 ± 5.6 mL·kg-1·min-1).
Effective Dosage
Not specified (isocaloric-matched diets with macronutrient manipulation).
Duration
7-day intervention diet (total study duration: 21 days).
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
high-protein, reduced-carbohydrate (PRO) diet | increase | AMPK expression | 16 trained endurance runners | 1.37-fold increase | resulted in a modest change | #1 |
high-protein, reduced-carbohydrate (PRO) diet | increase | fat oxidation | 16 trained endurance runners | 0.29 ± 0.05 to 0.59 ± 0.05 g·min-1 | significant increase | #2 |
high-protein, reduced-carbohydrate (PRO) diet | decrease | time to exhaustion (TTE) | 16 trained endurance runners | 23.3% | significant reduction | #3 |
high-carbohydrate (CHO) diet | no change | sub-maximal fuel utilisation | 16 trained endurance runners | - | no change | #4 |
high-carbohydrate (CHO) diet | increase | time to exhaustion (TTE) performance | 16 trained endurance runners | 6.5% | significant increase | #5 |
high-carbohydrate (CHO) diet | increase | AMPK mRNA expression | 16 trained endurance runners | - | modest, but significant, increase | #6 |
high-carbohydrate (CHO) diet | increase | PPAR mRNA expression | 16 trained endurance runners | - | modest, but significant, increase | #7 |
high-carbohydrate (CHO) diet | increase | AMPK | 16 trained endurance runners | - | remaining significantly elevated | #8 |
high-carbohydrate (CHO) diet | increase | PPAR | 16 trained endurance runners | - | remaining significantly elevated | #9 |
Manipulating dietary macronutrient intake may modulate adaptive responses to exercise, and improve endurance performance. However, there is controversy as to the impact of short-term dietary modification on athletic performance. In a parallel-groups, repeated measures study, 16 trained endurance runners (maximal oxygen uptake (V˙O2max): 64.2 ± 5.6 mL·kg-1·min-1) were randomly assigned to, and provided with, either a high-protein, reduced-carbohydrate (PRO) or a high-carbohydrate (CHO) isocaloric-matched diet. Participants maintained their training load over 21-consecutive days with dietary intake consisting of 7-days habitual intake (T1), 7-days intervention diet (T2) and 7-days return to habitual intake (T3). Following each 7-day dietary period (T1-T3), a micro-muscle biopsy was taken for assessment of gene expression, before participants underwent laboratory assessment of a 10 km treadmill run at 75% V˙O2max, followed by a 95% V˙O2max time to exhaustion (TTE) trial. The PRO diet resulted in a modest change (1.37-fold increase, p = 0.016) in AMPK expression, coupled with a significant increase in fat oxidation (0.29 ± 0.05 to 0.59 ± 0.05 g·min-1, p < 0.0001). However, a significant reduction of 23.3% (p = 0.0003) in TTE post intervention was observed; this reverted back to pre levels following a return to the habitual diet. In the CHO group, whilst no change in sub-maximal fuel utilisation occurred at T2, a significant 6.5% increase in TTE performance (p = 0.05), and a modest, but significant, increase in AMPK (p = 0.042) and PPAR (p = 0.029) mRNA expression compared to T1 were observed; with AMPK (p = 0.011) and PPAR (p = 0.044) remaining significantly elevated at T3. In conclusion, a 7-day isocaloric high protein diet significantly compromised high intensity exercise performance in trained runners with no real benefit on gene markers of training adaptation. A significant increase in fat oxidation during submaximal exercise was observed post PRO intervention, but this returned to pre levels once the habitual diet was re-introduced, suggesting that the response was driven via fuel availability rather than cellular adaptation. A short-term high protein, low carbohydrate diet in combination with endurance training is not preferential for endurance running performance.