Most bodybuilders always take a pre-workout protein drink before hitting the gym, but new research shows that it may be better to train fasted. Researchers compared the responses of growth factors and signaling pathways involved in muscle protein synthesis after a resistance training session performed in either the fasted or fed state.   

Six young male subjects participated in two experimental sessions separated by three weeks. In each session, they performed standardized resistance training. After the sessions, they received during a four-hour recovery period, 6ml/kg per body weight per hour a solution containing carbohydrates (50g/l), protein hydrolysate (33g/l), and leucine (16.6g/l).  

On one occasion, the resistance exercise session was performed after the intake of a carbohydrate-rich breakfast, whereas in the other session they remained fasted. Needle biopsies from vastus lateralis muscle were obtained before (rest), and one hour and four hours after exercise.

P70s6 is referred to as an activator of muscle growth and often used in studies to determine the latter. The results show the fasted group had twice the levels of p70s6k in comparison to the other group at the one-hour post-workout mark.   

The results indicate that prior fasting may stimulate the anabolic response to ingestion of the carbohydrate/protein/leucine mixture following a heavy resistance-training session.