The effect of post-exercise drink macronutrient content on appetite and energy intake

Carbohydrate and protein ingestion post-exercise are known to facilitate muscle glycogen resynthesis and protein synthesis, respectively, but the effects of post-exercise nutrient intake on subsequent appetite are unknown. This study aimed to investigate whether protein induced satiety that has been reported at rest was still evident when pre-loads were consumed in a post-exercise context. Using a randomised, double blind, crossover design, 12 unrestrained healthy males completed 30min of continuous cycling exercise at ~60% VO₂peak, followed by five, 3min intervals at ~85% VO₂peak. Ten min post-exercise, subjects consumed 500ml of either a low energy placebo (15kJ) (PLA); a 6% whey protein isolate drink (528kJ) (PRO); or a 6% sucrose drink (528kJ) (CHO). Sixty min after drink ingestion, a homogenous ad-libitum pasta lunch was provided and energy intake at this lunch was quantified. Subjective appetite ratings were measured at various stages of the protocol. Energy consumed at the ad-libitum lunch was lower after PRO (5831±960kJ) than PLA (6406±492kJ) (P<0.05), but not different between CHO (6111±901kJ) and the other trials (P>0.315). Considering the post-exercise drink, total energy intake was not different between trials (P=0.383). There were no differences between trials for any of the subjective appetite ratings. The results demonstrate that where post-exercise liquid protein ingestion may enhance the adaptive response of skeletal muscle, this may be possible without affecting gross energy intake relative to consuming a low energy drink.