Acute Effect of Post-Resistance Exercise Milk-Based Supplement on Substrate Oxidation and Fat Mobilization in Older Men: A Pilot Study

Background: It was reported that cow’s milk-based supplementation after resistance training reduced fat mass in older men. The reasons behind this beneficial impact remain to be elucidated. Hence, the aim of this study was to determine the effect of a cow’s milk-based supplementation after resistance exercise on lipid oxidation and systemic fat mobilization in older men. Methods: Older men (age range: 60–75 years) participated in a randomized, double-blind, crossover study with the two following conditions: (1) Resistance exercise + Cow’s milk (C-milk) and (2) Resistance exercise + Rice milk (R-milk; isocaloric control). During a 180-min post-exercise period, energy expenditure, substrate oxidation (indirect calorimetry), plasma levels of glycerol (systemic fat mobilization) and free fatty acids (FFA) were measured. Results: During the 180-min post-exercise period, lipid oxidation remained similar in both conditions. Glycerol levels decreased similarly in C-milk and R-milk (p ≤ 0.045). Although FFA levels increased progressively from 60 min to 180 min post-exercise in both conditions, the magnitude of changes (∆) was greater in C-milk condition between 60 and 120 min post-exercise (p < 0.018). Conclusions: These results do not support a large impact of cow’s milk supplementation after resistance exercise on lipid oxidation and systemic fat mobilization. However, the greater increase in FFA levels suggests that re-esterification may be influenced.