Effect of dietary fat level on performance and metabolism in trained male and female runners

Low dietary fat has been recommended for athletes to increase performance, bul recent itudia with animali and human suggest that a moderately high flu did may be beneficial for endurance athletes. We ttudied the effects thai tow, recommended and high fat level died have on performance and metabolic profilet in highly trained runner (40mi/wk). Twelve subjects (6♂, 36y and 6♀, 32y) ale dicts of 15, 30 and 45% at for 4 wt. successively. Thirteen subjects (♂, 39y and 7♀, 35y) could not increase fat inuko to 45% and remained at 30% for 4 additional wks. Endurance and VO₂ max teating were done at the end each 4 wfca with blood drawn before and after both tau. Plasma levels of lactaie, pyruvate, glucose, triglycese and glycerol were measured. Endurance time, anaerobic power and leg force increased from the low ft to recommended fat diet by 14, 9 and 11%, respectively. No differences were seen in plasma levels except pyruvate which wai higher after the VO2 max test and triglycérides which were higher on the recommended fat diet during the endurance test. The only significant diflercncej observed with the subjects that increased their dietary fat intake to 45% were higher planna pyruvate (46%) after the endurance test and a longer VO2 max test time (4%). Subjects mat remained on the recommended fat diet had lower post VO2 max lactates and slightly higher VO₂ max values (L/min, 5%). Body weight and % body fat (♂: 57 kg. 19% and C: 71kg, 16%), and plasma glucose and glycerol responses during exercise did not change after any diet. These results suggest that a low fat may be detrimental to performance and that a higher fat diet may result in more energy substrate availability with a lower lactate to pyruvate ratio.