Effects on Hormone Release and Selected Compounds-Sports

By:Robert Baird Baird




Likewise in its infancy stages, research on the effects of macronutrient manipulation on hormone release and other compounds (i.e., enzyme activity) has commenced in recent years. The surging interest in this area of investigation has primary implications on potential athletic performance enhancement and recovery, body composition improvement, and effects on substrate use during exercise and rest. For example, some studies have explored the effects of dietary manipulation on the hormones testosterone, growth hormone, and insulin, which promote strength and muscular increases. Thus, such research triggers particular interest for those involved in strength/power sports or who wish to increase strength and muscularity through resistance training. Other studies have examined the effect of macronutrient manipulation on such factors as fat loss and metabolic rate (which may be related to hormones and other compounds), with considerable implications for those intending to improve body composition. Again, although no definite conclusions can be made, initial research has certainly sparked additional interest in this realm of physique and athletic enhancement.

The goal of many athletes and exercise enthusiasts is to increase muscular strength and size; therefore, optimal conditions for recovery following training sessions are necessary. Optimal recovery is mandatory because heavy­resistance exercise damages certain muscle fibers that must subsequently undergo remodeling. Recovery, in fact, involves the function of many physiological processes that are influenced by the availability of specific hormones and nutrients. Together, hormones, nutrients, and other growth factors regulate this remodeling of skeletal muscle proteins.

Independent of exercise, nutrients also have the power to influence hormonal concentrations that may positively affect athletes and those who wish to improve body composition. A simple increase in caloric intake above energy requirements enhances growth hormone, testosterone, and insulin-like growth factor-I (IGF-I) concentrations In contrast, energy and protein restriction has produced negative effects on serum IGF-I concentrations, and diets with low percentages of dietary fat are associated with lower testosterone concentrations.

Research regarding nutritional supplementation's effects on the hormonal response to resistance exercise has been performed by Chandler et al who demonstrated that insulin and growth hormone (GH) release can be influenced by the diet. The researchers concluded that, following a resistance training session, insulin and growth hormone concentrations were significantly higher and testosterone concentrations were lower when subjects consumed a protein-carbohydrate supplement immediately before and 2 hours after the workout. In agreement with these findings was a study by Fahey et al who reported a significant increase in insulin concentrations following exercise when subjects consumed a protein­carbohydrate supplement 30 minutes before and intermittently during a weight-training session.

A similar study by Kraemer et al also coincided with previous findings, and in this case involved 3 consecutive days of resistance training. The investigators found that ingesting a protein-carbohydrate supplement (33% protein or ~ 30 g; 67% carbohydrate or ~60 g) 2 hours before and immediately after workouts significantly increased serum concentrations of insulin, growth hormone, and IGF-I while testosterone decreased below resting levels. The authors predicted that these responses could enhance glycogen and protein synthesis during recovery. They also proposed diet-related factors that could explain the drop in testosterone concentrations that occurred in this and aforementioned studies. A primary factor, according to the authors, was that percent dietary fat ranged from nonexistent to 14% in the supplements administered in the studies, which correlates with decreased testosterone levels Secondly, the protein-to­carbohydrate ratio during supplementation was significantly higher than during the placebo conditions. This is also a potential factor because a high protein-to­carbohydrate ratio is also associated with lower testosterone concentrations in healthy active men.

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