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Manipulation of Dietary Intake on Changes in Circulating Testosterone Concentrations.
Zamir, A, Ben-Zeev, T, Hoffman, JR
Nutrients. 2021;13(10)
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Androgens, like testosterone, are steroid hormones commonly associated with reproduction. However, they also govern metabolic functions, body composition and growth. Higher levels of circulating androgens enhance athletic performance by supporting metabolic activities such as protein production, regeneration and growth and by inhibiting breakdown processes. Manipulating testosterone to enhance athletic performance without the use of anabolic steroids hormones has been of much interest. As macro-and micronutrients can influence androgen hormones, this review examined whether specific energy and nutrient intake can ‘naturally’ manipulate testosterone levels. The authors describe the metabolic functions of testosterone before exploring the current evidence on selected plant extracts and nutrients and their impact on aromatase activity. Inhibiting aromatase can prevent androgens from being converted into oestrogen and thus may help to raise circulating androgens. Discussed are a range of plant-derived compounds, flavonoids, macronutrients and micronutrients (Vitamin D, Zinc and Magnesium) and their impact on testosterone levels. The authors conclude that the nutrients discussed have some supportive evidence, yet overall findings are inconclusive due to limited studies. Regarding macronutrients more research is available, and the evidence supports that low energy intake negatively impacts testosterone levels and performance. Whereby supplementation of vitamins crucial to testosterone production seems to provide value in cases of deficiency further research is required. This article yields an overview of plant compounds, macro-and micronutrients and their potential impact on circulating testosterone levels. While low energy intake and nutrient deficiencies appears to be unfavourable, the absence of clear evidence on other compounds would warrant further case-specific investigations.
Abstract
Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.
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Time-restricted eating effects on performance, immune function, and body composition in elite cyclists: a randomized controlled trial.
Moro, T, Tinsley, G, Longo, G, Grigoletto, D, Bianco, A, Ferraris, C, Guglielmetti, M, Veneto, A, Tagliabue, A, Marcolin, G, et al
Journal of the International Society of Sports Nutrition. 2020;17(1):65
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Adequate nutrition is important for elite athletes, as nutrient availability influences energy expenditure, body composition, performance and exercise-induced immune responses. Time-restricted eating (TRE) is a form of intermittent fasting that has received much interest in recent years. Previous research of TRE suggested beneficial effects on performance in untrained individuals, by allowing weight loss whilst maintaining muscle functions. These qualities are of interest for endurance cyclists hence the authors of this study sought to investigate the impact of TRE in elite cyclists. Sixteen under-23 year old, elite cyclists were randomly assigned to eat within a TRE window of 8-hr or 15hr window during a 4-week, high-level endurance training phase. Both groups consumed their full estimated energy needs and markers such as fat and fat-free mass, VO2 max, basal metabolism, blood counts, anabolic hormones and inflammatory markers were measured. As a result, TRE produced weight loss, improved body composition and increased peak power output in relation to body weight without compromising aerobic performance. Furthermore, the TRE pattern proved helpful in mitigating some of the exercise-induced suppressions of the immune system. The authors concluded that TRE could be considered as part of a performance nutrition plan in endurance athletes. Particularly where there is a need to reduce body fat mass or for the management of training-induced depression of the immune system and associated respiratory infection susceptibility. This can be of clinical relevance in the support of endurance athletes.
Abstract
BACKGROUND Although there is substantial interest in intermittent fasting as a dietary approach in active individuals, information regarding its effects in elite endurance athletes is currently unavailable. The present parallel randomized trial investigated the effects of a particular intermittent fasting approach, called time-restricted eating (TRE), during 4 weeks of high-level endurance training. METHODS Sixteen elite under-23 cyclists were randomly assigned either to a TRE group or a control group (ND). The TRE group consumed 100% of its estimated daily energy needs in an 8-h time window (from 10:00 a.m. to 6:00 p.m.) whilst energy intake in the ND group was distributed in 3 meals consumed between 7:00 a.m. and 9:00 p.m. Fat and fat-free mass were estimated by bioelectrical impedance analysis and VO2max and basal metabolism by indirect gas analyzer. In addition, blood counts, anabolic hormones (i.e. free testosterone, IGF-1) and inflammatory markers (i.e. IL-6, TNF-α) were assessed. RESULTS TRE reduced body weight (- 2%; p = 0.04) and fat mass percentage (- 1.1%; p = 0.01) with no change in fat-free mass. Performance tests showed no significant differences between groups, however the peak power output/body weight ratio (PPO/BW) improved in TRE group due to weight loss (p = 0.02). Free testosterone and IGF-1 decreased significantly (p = 0.01 and p = 0.03 respectively) in TRE group. Leucocyte count decreased in ND group (p = 0.02) whilst the neutrophils-to-lymphocytes ratio (NLR) decreased significantly (p = 0.03) in TRE group. CONCLUSIONS Our results suggest that a TRE program with an 8-h feeding window elicits weight loss, improves body composition and increases PPO/BW in elite cyclists. TRE could also be beneficial for reducing inflammation and may have a protective effect on some components of the immune system. Overall, TRE could be considered as a component of a periodized nutrition plan in endurance athletes. TRIAL REGISTRATION This trial was retrospectively registered at clinicaltrials.gov as NCT04320784 on 25 March 2020.