EFFECTS OF A FAT-RICH DIET ON MAXIMAL OXYGEN UPTAKE AND TIME-TO-EXHAUSTION IN MALE TRIATHLETES.

Abstract

1142 Muoio et al. ( MSSE 26, 81-88, 1994) reported that a fat-rich diet improved VO2max and time-to-exhaustion (TEx) in male athletes. This study used similar dietary treatments in a counter-balanced order. Subjects were five male ironman triathletes (mean ± SEM, 33.8 ± 4.3 yrs, 75.6 ± 2.8 kgs, and 177.0 ± 4.1 cm). The percent of energy from CHO, fat and protein was 57/24/17, 50/38/12 and 73/15/12 for their normal (N), fat-rich (F), and high CHO (C) diets. Subjects consumed the two experimental diets (F and C) (≈3600 kcals/d) for 7 days prior to testing. VO2max and TEx trials (at 60% VO2max) were performed on a cycle ergometer. Data were analyzed using a repeated measures ANOVA. VO2max values were not significantly different between the C vs F ( p) = 0.57): N = 58.7± 2.0, F = 60.4 ± 1.5, and C = 61.2 ± 2.0 ml·kg-1·min-1. Cycling TEx were: N = 134.0± 25.3, F = 191.9 ± 30.8, C = 163.5 ± 23.9 min. The TEx was significantly different between the N and F trials ( p <0.05), no differences were found between the C and F trials ( p =.25). Mean respiratory exchange ratios (RER) for six relative time periods for each diet were: N =.92,.90,.88,.87,.87 and.86; F =.88,.87,.85,.84,.84 and.84; C=.90,.89,.89,.88,.87 and.86. RER were not significantly different between the F and C trials ( p = 0.07). Mean percent kcals utilized from fat(from RER) were: F = 48.3 and C = 38.3%; mean percent kcals from CHO were: F = 51.7 and C = 61.7%; these values were not significantly different between trials. There were no differences in ratings of perceived exertion between trials. It was concluded that a fat-rich diet did not improve VO2max, TEx or affect substrate utilization compared to a high CHO diet for triathletes cycling at 60% VO2max.