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

Abstract

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 x kg(-1) x d(-1) carbohydrate; 1.2 +/- 0.3 g x kg(-1) x d(-1) fat; 1.3 +/- 0.4 g x kg(-1) x d(-1) protein) or H-Pro (4.9 +/- 1.8 g x kg(-1) x d(-1); 1.3 +/- 0.3 g x kg(-1) x d(-1); 3.3 +/- 0.4 g x kg(-1) x 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.

An isoenergetic high-protein, moderate-fat diet does not compromise strength and fatigue during resistance exercise in women

“…The slight (NS) decrease in resting diastolic arterial pressure after the high-protein diet is similar to that reported previously (7) .…”

“…There is evidence that high-protein diets induce a number of favourable changes along with weight loss (reduction in body fat, improvement in lipidaemic and glycaemic profiles and resting blood pressure) (2,4) . The addition of exercise (aerobic and/or resistance) to a high-protein diet had additive effects on body composition during weight loss (5) .Despite the popularity of high-protein diets, few studies have investigated their effects on exercise performance (6,7) . These studies reported that a 7 d high-protein diet decreased endurance (aerobic) performance of recreational and trained athletes.…”

“…Despite the popularity of high-protein diets, few studies have investigated their effects on exercise performance (6,7) . These studies reported that a 7 d high-protein diet decreased endurance (aerobic) performance of recreational and trained athletes.…”

Optimal Nutrition for Endurance Exercise: A Systematic Review

“…Following a high-protein diet compared to high-carbohydrate diet had either a neutral [14] or negative [13] effect on timed trials compared to a high carbohydrate diets. Interestingly, athletes who supplemented with almonds exercised longer than those supplemented with isocaloric cookies, despite the lower carbohydrate content of the almonds [16].…”

“…Macdermid et al investigated the effect of 7 days of a high carb versus a high protein diet on long distance time trial performance in 7 competitive cyclists [13]. They found superior time trial performance in the high carbohydrate group.…”