Testosterone is a steroid hormone secreted from the Leydig cells of the testes that has both anabolic and anticatabolic effects upon muscle tissue. Dietary nutrients, in particular fat, have been shown to affect testosterone. Individuals consuming a diet containing about 20% fat compared with a diet containing 40% fat have significantly lower concentrations of testosterone.
Also, replacing dietary carbohydrate with protein has been shown to decrease testosterone concentrations. Men consuming a vegetarian or meatless diet have lower circulating concentrations of testosterone compared with men consuming a mixed Western or a high-meat diet.
These studies indicate that the distribution of macronutrients has a significant influence on testosterone concentrations. The specific type or quality of macronutrient may also impact testosterone independent of a change in diet composition. Volek et al. reported significant positive correlations between dietary fat, specifically saturated and monounsaturated fatty acids, and resting testosterone concentrations in a group of young resistance-trained men. Raben et al. reported a significant decrease in resting testosterone concentrations and an attenuation in the exerciseinduced increase in testosterone in male endurance athletes who switched from a meat-rich diet to a lacto-ovo vegetarian diet. The diets contained equal percentages of calories derived from protein, carbohydrate, and fat; however, the source of protein in the vegetarian diet was derived mainly from vegetable sources (83%), whereas the mixed diet contained significantly less vegetable protein (35%).
The exact mechanism linking nutrition to testosterone is unknown. Increasing anabolic hormone concentrations at rest, after a meal, or after exercise may enhance adaptations to resistance training. Manipulation of the distribution of carbohydrate and fat in the diet may alter the hormonal environment (e.g., habitual consumption of a fatrich diet has been shown to elevate fasting testosterone and growth hormone concentrations). Thus, macronutrient manipulation should be considered a potential strategy to enhance the adaptations to exercise training programs. However, until further research is performed that documents specific training outcome markers in athletes under a variety of dietary regimens, generalizations should be made with caution.
Practically no information exists regarding the practical application of increasing circulating anabolic hormones on muscle size and strength; the potential differential effects in different populations (e.g., men vs. women, young vs. old, trained vs. sedentary), the interaction of different hormone responses; the effects at the target tissue (e.g., potential down-regulation of receptors); and the impact of “nutrient cycling”(e.g., consuming a carbohydrate-rich diet followed by a fat-rich diet).Considering the enormous complexity in which the endocrine system operates in the regulation of cellular function and the diverse mechanisms that control homeostasis, the optimal dietary strategy to The total daily energy intake in this scenario then becomes 2015 kcal (524/0.26). In this instance, carbohydrates will comprise 50% of the total (l008 kcal, 252 g), and fat, 24% (484 kcal, 54 g). In TABLE , a sample diet, with a goal of physique enhancement and weight maintenance, is provided for this individual.
Note that the dietary regimen outlined in contains five meals per day. This was included as a possible means to stimulate metabolic rate increases via an increased thermic effect of food consumption. It is recommended that consuming multiple daily meals should be a method used regardless of physique modification goals. In this way, potential enhancements in the efficiency of the body’s metabolic processes may ensue. It cannot be stressed enough that the information provided and are recommendations based on limited research and the authors’ discretion. Individual tinkering of the daily caloric total is likely for the achievement of desired goals. For example, rapid weight loss is a sign that caloric intake is deficient, and subsequent losses in weight are more likely the result of water and lean tissue losses than fat. In this case, a slight increase in daily calories is necessary, as weight loss (and gain) should be a consistent, gradual process. Similarly, frequent (roughly every 2 weeks) reassessments of body weight and composition should be performed, and appropriate dietary modifications should be implemented based on these findings.
Insulin is a peptide hormone secreted by the pancreas, which plays a critical role in the regulation of blood glucose levels and stimulation of amino acid uptake for incorporation into skeletal muscle proteins. Carbohydrate ingestion leads to an increase in blood glucose and a relatively similar increase in insulin concentrations. A meal rich in fat results in lower insulin responses compared with meals rich in either carbohydrate or protein. Also, there is a decrease in resting glucose and insulin concentrations in response to 3 to 4 days of a eucaloric low-carbohydrate diet high in fat and low in carbohydrate. Three weeks of a low-carbohydrate diet may significantly lower resting insulin but not glucose concentrations in healthy men. Although insulin stimulates protein synthesis, maximizing insulin concentrations may not be advantageous because of the potent antilipolytic (Le., blocks mobilization of fat from storage) and lipogenic (Le., promotes storage of fat) effects of insulin.