Effect of fat and protein intake on changes in circulating testosterone concentrations. Although evidence points to a positive effect of dietary fat on circulating testosterone concentrations, it should not be dismissed that fat is not the optimal fuel source for athletes participating in strength/power sports 83,90,91,92. It has been suggested that increases in testosterone concentrations resulting from a KD are related to the high dietary intake of cholesterol . Additional research reported significant decreases in testosterone concentrations in long-distance runners who were categorized as "low energy available" (−1) compared to runners categorized as "moderate energy available" (30–45 kcal·kg FFM·day−1) . Hu and colleagues observed a significant decrease in testosterone concentrations when dietary macronutrient intake was reduced. Consuming foods or dietary supplements containing nutrients with aromatase inhibitors may provide an ergogenic effect by inhibiting the conversion of testosterone to estradiol, indirectly increasing testosterone concentrations. Certain food types such as protein and complex carbs have a higher thermic effect than fats or simple carbs because your body must work harder to break those foods down, thus spending more energy and burning more calories. Low-grade chronic inflammation has been shown to decrease testosterone concentrations by suppressing testosterone secretion from Leydig cells, resulting in both an inhibitory effect on LH secretion and reduced LH sensitivity at the Leydig cell 183,184. Considering that testosterone concentrations can be strongly influenced by oxidative stress , it is possible that magnesium’s role in decreasing oxidative stress may provide the stimulus to maintain testosterone concentrations during periods of oxidative stress. Whether zinc supplementation is effective only during periods of zinc deficiency or whether it can augment normal testosterone concentrations regardless of baseline concentrations is not well understood. Several studies have shown that zinc supplementation can restore testosterone concentrations to their normal physiological range 153,154,158. Zinc deficiency can impair testosterone synthesis and has been demonstrated to correlate with reductions in testosterone concentrations 153,154,155. Furthermore, the effect of vitamin D supplementation on altering resting testosterone concentrations is still not well understood and requires further research. While calories provide a useful framework for energy balance, the thermic effect of food (TEF) varies significantly by macronutrient. However, evidence supporting any benefits of supplementing with these micronutrients to augment testosterone concentrations is lacking. Most circulating testosterone is bound to SHBG; however, the bioavailability of testosterone is related to the free testosterone concentrations, which is only a fraction of circulating testosterone . The main effect of protein on energy balance is thought to be DIT related satiety. Protein plays a key role in food intake regulation through satiety related to DIT . The studies reporting a DIT value below 10% measured DIT as the increase in energy expenditure above basal fasting level over an interval of 4 to 5.5 h after the meal. Reported DIT values for separate nutrients are 0 to 3% for fat, 5 to 10% for carbohydrate, 20 to 30% for protein , and 10 to 30% for alcohol . As such, the amount of food ingested quantified as the energy content of the food is a determinant of DIT. In a regression analysis of the remaining 19 studies, the protein fraction of the food came out as significant determinant of DIT. For a comparison of DIT between studies as a function of the nutrient composition of the test food consumed, the energy content of the test food was divided by the length of the measurement interval after food consumption and expressed in MJ/h. NF-κB inhibits the activation of steroidogenic-enzyme genes such as Nur77 and SF-1, which regulate steroidogenesis (biosynthesis of testosterone from cholesterol) in the Leydig cells . In contrast, normal magnesium levels can prevent oxygen radical formation by removing free radicals and inhibiting xanthine oxidase and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase elevations . Magnesium deficiency has been demonstrated to increase production of oxygen free radicals, increase oxidative tissue damage, decrease antioxidant enzyme activity, decrease cellular antioxidant levels, and increase oxygen peroxide production 176,177,178. Varying factors affect TEF, primarily the portion size of your meal and its macronutrient composition – protein, carbohydrates and fats – along with your age. So, for example, if you expend 2000 calories in a day, around 200 of those will be burned just from eating food. Factors such as age, activity levels, overall meal size, the breakdown of macronutrients at each meal, and meal frequency can all influence the thermic effect of food. While high thermic foods increase your metabolic rate, the effects are temporary. The sampling method of this study was non-probability volunteer sampling. This was a cross-sectional study with 125 Taiwanese males aged 20‒64 years. We hypothesized that obesity might affect not only the male sex hormone, T, but also nutrient metabolism (e.g., iron and glucose), and alterations in nutrient metabolism may contribute to the bidirectional relationship between obesity and the male sex hormone, T. Overall, the effect of CHO intake on androgen may differ between genders. A 10-day fast in obese men resulted in a significant fall in serum T levels, regardless of whether there was carbohydrate (CHO) supplementation (15 or 45 g/day), and T levels increased to normal during the re-feeding (1500 Kcal/day) period .
