A Whey-Supplemented, High-Protein Diet versus a High-Carbohydrate Diet: Effects on Endurance Cycling Performance

in International Journal of Sport Nutrition and Exercise Metabolism
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This study compared a training diet recommended for endurance athletes (H-CHO) with an isoenergetic high protein (whey supplemented), moderate carbohydrate (H-Pro) diet on endurance cycling performance. Over two separate 7-d periods subjects (n = 7) ingested either H-CHO (7.9 ± 1.9 g · kg−1 · d−1 carbohydrate; 1.2 ± 0.3 g · kg−1 · d−1 fat; 1.3 ± 0.4 g · kg−1 · d−1 protein) or H-Pro (4.9 ± 1.8 g · kg−1 · d−1; 1.2 ± 0.3 g · kg−1 · d−1; 3.3 ± 0.4 g · kg−1 · d−1) diet in a randomized, balanced order. On day 8 subjects cycled (self-paced) for a body weight dependent (60 kJ/bm) amount of work. No differences occurred between energy intake (P = 0.422) or fat intake (P = 0.390) during the two dietary conditions. Performance was significantly (P = 0.010) impaired following H-Pro (153 ± 36) compared with H-CHO (127 ± 34 min). No differences between treatments were observed for physiological measures taken during the performance trials. These results indicate an ergolytic effect of a 7-d high protein diet on self-paced endurance cycling performance.

Macdermid is with Universal College of Learning, Palmerston North, New Zealand. Stannard is with the Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand.