Objective: The objective of this study was to compare the chronic effects of different whey protein forms on body composition and performance when supplemented with resistance training.
Methods: Resistance-trained men (N = 56, 21.4 ± 0.4 years, 79.5 ± 1.0 kg) participated in an 8-week resistance training regimen (2 upper-body sessions and 2 lower-body sessions per week) and received one of 4 double-blinded treatments: 30 g/serving carbohydrate placebo (PLA) or 30 g/serving protein from either (a) 80% whey protein concentrate (WPC), (b) high-lactoferrin-containing WPC (WPC-L), or (c) extensively hydrolyzed WPC (WPH). All subjects consumed 2 servings of treatment per day; specifically, once immediately before and after training and between meals on nontraining days. Blood collection, one repetition maximum (1RM) testing for bench press and hack squat, and body composition assessment using dual-energy x-ray absorptiometry (DXA) occurred prior to training and 48 hours following the last training session.
Results: Total body skeletal muscle mass increased in all groups (p < 0.0125). There were similar between-group increases in upper-body (4%-7%, analysis of covariance [ANCOVA] interaction p = 0.73) and lower-body (24%-35%, ANCOVA interaction p = 0.85) 1RM strength following the intervention. Remarkably, WPH reduced fat mass (-6%), which was significantly different from PLA (+4.4%, p < 0.0125). No time or between-group differences were present for serum markers of health, metabolism, or muscle damage, with the exception of blood urea nitrogen being significantly lower for WPH than WPC (p < 0.05) following the intervention.
Conclusions: WPH may augment fat loss but did not provide any other advantages when used in combination with resistance training. More mechanistic research is needed to examine how WPH affects adipose tissue physiology.
Keywords: body composition; exercise; metabolism; sports nutrition; supplements and functional foods.