title: Effect of dietary fat on serum and intramyocellular lipids and running performance.
abstract: OBJECTIVE
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, USA. enette@uwyo.edu
authors.forename: D Enette
authors.initials: DE
authors.lastname: Larson-Meyer
authors.forename: Olga N
authors.initials: ON
authors.lastname: Borkhsenious
authors.forename: Jon C
authors.initials: JC
authors.lastname: Gullett
authors.forename: Ryan R
authors.initials: RR
authors.lastname: Russell
authors.forename: Michaela C
authors.initials: MC
authors.lastname: Devries
authors.forename: Steven R
authors.initials: SR
authors.lastname: Smith
authors.forename: Eric
authors.initials: E
authors.lastname: Ravussin
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D018752:Diet, Fat-Restricted; D004041:Dietary Fats; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*
chemical_list: D004041:Dietary Fats; D006003:Glycogen