PURPOSE: This study evaluated whether lowering IMCL stores via 3-d consumption of very-low-fat (LFAT) diet impairs endurance performance relative to a moderate-fat diet (MFAT), and whether such a diet unfavorably alters lipid profiles.

METHODS: Twenty-one male and female endurance-trained runners followed a controlled diet and training regimen for 3 d prior to consuming either a LFAT (10% fat) or MFAT (35% fat) isoenergetic diet for another 3 d in random crossover fashion. On day 7, runners followed a glycogen normalization protocol (to equalize glycogen stores) and then underwent performance testing (90-min preload run at 62 +/- 1% VO2max followed by a 10-km time trial) on the morning of day 8. Muscle biopsies obtained from vastus lateralis before and after performance testing were analyzed for IMCL (via electron microscopy) and glycogen content (via enzymatic methodology).

RESULTS: Despite approximately 30% lower IMCL (0.220 +/- 0.032% LFAT, 0.316 +/- 0.049% MFAT; P = 0.045) and approximately 22% higher muscle glycogen stores at the start of performance testing (P = 0.10), 10-km performance time was not significantly different following the two diet treatments (43.5 +/- 1.4 min LFAT vs 43.7 +/- 1.2 min MFAT). However, LFAT produced less favorable lipid profiles (P < 0.01) by increasing fasting triglycerides (baseline = 84.9 +/- 8.6; LFAT = 118.7 +/- 10.0 mg.dL(-1)) and the total cholesterol:HDL cholesterol ratio (baseline = 3.42 +/- 0.13:1; LFAT = 3.75 +/- 0.20:1), whereas MFAT lowered triglycerides (baseline = 97.5 +/- 12.2; MFAT = 70.9 +/- 7.1 mg.dL(-1)) and the total cholesterol:HDL cholesterol ratio (baseline = 3.47 +/- 0.18:1; MFAT = 3.33 +/- 0.14:1).

CONCLUSION: The results suggest that reducing IMCL via 3-d consumption of a LFAT diet does not impair running performance lasting a little over 2 h (compared with 3-d consumption of a MFAT diet plus 1-d glycogen normalization), but that even short-term consumption of a LFAT diet may unfavorably alter serum lipids, even in healthy, endurance-trained runners.

Item Type:	Refereed Article
Keywords:	intramyocellular lipids and running performance
Research Division:	Medical and Health Sciences
Research Group:	Human Movement and Sports Science
Research Field:	Exercise Physiology
Objective Division:	Health
Objective Group:	Health and Support Services
Objective Field:	Health and Support Services not elsewhere classified
Author:	Russell, R (Dr Ryan Russell)
ID Code:	98043
Year Published:	2008
Web of Science® Times Cited:	10
Deposited By:	Menzies Institute for Medical Research
Deposited On:	2015-01-29
Last Modified:	2015-04-21
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