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ObjectivesWe systemically reviewed the literature to assess how long-term testosterone suppressing gender-affirming hormone therapy influenced lean body mass (LBM), muscular area, muscular strength and haemoglobin (Hgb)/haematocrit (HCT).DesignSystematic review.Data sourcesFour databases (BioMed Central, PubMed, Scopus and Web of Science) were searched in April 2020 for papers from 1999 to 2020.Eligibility criteria for selecting studiesEligible studies were those that measured at least one of the variables of interest, included transwomen and were written in English.ResultsTwenty-four studies were identified and reviewed. Transwomen experienced significant decreases in all parameters measured, with different time courses noted. After 4 months of hormone therapy, transwomen have Hgb/HCT levels equivalent to those of cisgender women. After 12 months of hormone therapy, significant decreases in measures of strength, LBM and muscle area are observed. The effects of longer duration therapy (36 months) in eliciting further decrements in these measures are unclear due to paucity of data. Notwithstanding, values for strength, LBM and muscle area in transwomen remain above those of cisgender women, even after 36 months of hormone therapy.ConclusionIn transwomen, hormone therapy rapidly reduces Hgb to levels seen in cisgender women. In contrast, hormone therapy decreases strength, LBM and muscle area, yet values remain above that observed in cisgender women, even after 36 months. These findings suggest that strength may be well preserved in transwomen during the first 3 years of hormone therapy.

Lifestyle choices influence 20–40 % of adult peak bone mass. Therefore, optimization of lifestyle factors known to influence peak bone mass and strength is an important strategy aimed at reducing risk of osteoporosis or low bone mass later in life. The National Osteoporosis Foundation has issued this scientific statement to provide evidence-based guidance and a national implementation strategy for the purpose of helping individuals achieve maximal peak bone mass early in life. In this scientific statement, we (1) report the results of an evidence-based review of the literature since 2000 on factors that influence achieving the full genetic potential for skeletal mass; (2) recommend lifestyle choices that promote maximal bone health throughout the lifespan; (3) outline a research agenda to address current gaps; and (4) identify implementation strategies. We conducted a systematic review of the role of individual nutrients, food patterns, special issues, contraceptives, and physical activity on bone mass and strength development in youth. An evidence grading system was applied to describe the strength of available evidence on these individual modifiable lifestyle factors that may (or may not) influence the development of peak bone mass (Table 1 ). A summary of the grades for each of these factors is given below. We describe the underpinning biology of these relationships as well as other factors for which a systematic review approach was not possible. Articles published since 2000, all of which followed the report by Heaney et al. [ 1 ] published in that year, were considered for this scientific statement. This current review is a systematic update of the previous review conducted by the National Osteoporosis Foundation [ 1 ]. Lifestyle Factor Grade Macronutrients  Fat D  Protein C Micronutrients  Calcium A  Vitamin D B  Micronutrients other than calcium and vitamin D D Food Patterns  Dairy B  Fiber C  Fruits and vegetables C  Detriment of cola and caffeinated beverages C Infant Nutrition  Duration of breastfeeding D  Breastfeeding versus formula feeding D  Enriched formula feeding D Adolescent Special Issues  Detriment of oral contraceptives D  Detriment of DMPA injections B  Detriment of alcohol D  Detriment of smoking C Physical Activity and Exercise  Effect on bone mass and density A  Effect on bone structural outcomes B Considering the evidence-based literature review, we recommend lifestyle choices that promote maximal bone health from childhood through young to late adolescence and outline a research agenda to address current gaps in knowledge. The best evidence (grade A) is available for positive effects of calcium intake and physical activity, especially during the late childhood and peripubertal years—a critical period for bone accretion. Good evidence is also available for a role of vitamin D and dairy consumption and a detriment of DMPA injections. However, more rigorous trial data on many other lifestyle choices are needed and this need is outlined in our research agenda. Implementation strategies for lifestyle modifications to promote development of peak bone mass and strength within one’s genetic potential require a multisectored (i.e., family, schools, healthcare systems) approach.

Exercise is an effective strategy for preventing and treating obesity and its related cardiometabolic disorders, resulting in significant loss of body fat mass, white adipose tissue browning, redistribution of energy substrates, optimization of global energy expenditure, enhancement of hypothalamic circuits that control appetite-satiety and energy expenditure, and decreased systemic inflammation and insulin resistance. Novel exercise-inducible soluble factors, including myokines, hepatokines, and osteokines, and immune cytokines and adipokines are hypothesized to play an important role in the body’s response to exercise. To our knowledge, no review has provided a comprehensive integrative overview of these novel molecular players and the mechanisms involved in the redistribution of metabolic fuel during and after exercise, the loss of weight and fat mass, and reduced inflammation. In this review, we explain the potential role of these exercise-inducible factors, namely myokines, such as irisin, IL-6, IL-15, METRNL, BAIBA, and myostatin, and hepatokines, in particular selenoprotein P, fetuin A, FGF21, ANGPTL4, and follistatin. We also describe the function of osteokines, specifically osteocalcin, and of adipokines such as leptin, adiponectin, and resistin. We also emphasize an integrative overview of the pleiotropic mechanisms, the metabolic pathways, and the inter-organ crosstalk involved in energy expenditure, fat mass loss, reduced inflammation, and healthy weight induced by exercise.

This study, designed to determine the relative degree of testosterone deficiency, estradiol deficiency, or both at which undesirable bodily changes occur, showed that some features of male hypogonadism are due to both androgen deficiency and estrogen deficiency. Testosterone therapy is prescribed for millions of men each year, and the number is increasing rapidly. Prescription sales of testosterone increased by 500% in the United States between 1993 and 2000. 1 Most testosterone prescriptions are written to treat nonspecific symptoms, such as fatigue or sexual dysfunction, when accompanied by testosterone levels below the laboratory reference range. Currently, testosterone levels that are at least 2 SD below the mean value for healthy young adults are classified as low. 1 , 2 Although convenient, this classification fails to consider the physiological consequences of specific testosterone levels. More than 80% of circulating estradiol in men . . .

Aims/hypothesis Asians have a propensity to develop type 2 diabetes with a lower BMI than Western populations. This discrepancy may be due to differences in body fat and muscle mass for a given BMI. However, unlike adiposity, it is unclear whether muscle mass affects the risk of type 2 diabetes in Asian populations. Methods We conducted a 2-yearly prospective assessment of 6895 participants who were free of diabetes at the baseline examination as part of the Korean Genome Epidemiology Study. The muscle mass index (MMI) was defined as the weight-adjusted appendicular skeletal muscle mass. Using Cox regression models, we evaluated the association between MMI and the risk of developing type 2 diabetes across sex-specific tertiles of MMI. Low muscle mass was defined as the sex-specific lowest tertile of MMI. Main covariates included age, sex, urban or rural residence, family history of diabetes, hypertension, smoking status, education level, monthly income, physical activity, alcohol consumption and diet. In addition, body fat mass, waist circumference and BMI were controlled as categorical variables. Obesity was defined as a BMI of ≥25 kg/m 2 or a waist circumference of ≥90 cm for men and ≥85 cm for women. Results During a median follow-up of 9.06 years, 1336 participants developed type 2 diabetes. At baseline, the mean age was 52.1 years and the mean BMI was 24.4 kg/m 2 . The mean MMI for men and women was 32.1% and 26.0%, respectively. There was an inverse association between MMI and the risk of type 2 diabetes. Multivariate-adjusted HRs for the risk of developing type 2 diabetes were 2.05 (95% CI 1.73, 2.43), 1.39 (95% CI 1.17, 1.66) and 1.0 from the lowest to highest sex-specific MMI tertile, with an HR of 1.35 (95% CI 1.26, 1.45) per SD decline in MMI. Further adjustments for fat mass, waist circumference and BMI as categorical variables did not modify the relationship (each p  < 0.01). In BMI-stratified analyses, the population-attributable fraction of the lowest tertile of MMI for developing type 2 diabetes was increased by 11.9% in the non-obese group and 19.7% in the obese group. Conclusions/interpretation Low muscle mass as defined by MMI was associated with an increased risk of type 2 diabetes, independent of general obesity, in middle-aged and older Korean adults.

The present systematic review aimed to compare the accuracy of Bioelectrical Impedance Analysis (BIA) and Bioelectrical Impedance Vector Analysis (BIVA) vs. reference methods for the assessment of body composition in athletes. Studies were identified based on a systematic search of internationally electronic databases (PubMed and Scopus) and hand searching of the reference lists of the included studies. In total, 42 studies published between 1988 and 2021 were included. The methodological quality was assessed using the Quality Assessment Tool for Observational Cohort and Cross-sectional Studies as recommended by the National Institute of Health. Twenty-three studies had an overall good rating in terms of quality, while 13 were rated as fair and 6 as poor, resulting in a low to moderate risk of bias. Fat mass was inconsistently determined using BIA vs. the reference methods, regardless of the BIA-technology. When using the foot to hand technology with predictive equations for athletes, a good agreement between BIA and the reference methods was observed for fat-free mass, total body, intra and extra cellular water. However, an underestimation in fat-free mass and body fluids was found when using generalized predictive equations. Classic and Specific BIVA represented a valid approach for assessing body fluids (Classic BIVA) and percentage of fat mass (Specific BIVA). The present systematic review suggests that BIA and BIVA can be used for assessing body composition in athletes, provided that foot-to-hand technology, predictive equations, and BIVA references for athletes are used.

This review focuses on the most important physical and physiological characteristics of karate athletes from the available scientific research. It has been established that karate's top-level performers require a high fitness level. Top-level male karate athletes are typified by low body fat and mesomorphic-ectomorphic somatotype characteristics. Studies dealing with body composition and somatotype of females are scarce. Aerobic capacity has been reported to play a major role in karate performance. It prevents fatigue during training and ensures the recovery processes during rest periods between two subsequent bouts of fighting activity within a fight and between two consecutive matches. It has been established that there is no significant difference between male and female kata (forms) and kumite (sparring/combat) athletes with regard to aerobic performance. Nevertheless, further studies are needed to support these findings. Concerning anaerobic performance, there is a difference in maximal power explored by the force-velocity test between national and international level karatekas (karate practitioners) but, for the maximum accumulated oxygen deficit test there is no difference between them. Muscle explosive power plays a vital role in a karateka's capacity for high-level performance. However, it has been revealed that vertical jump performance, maximal power and maximal velocity differed between national- and international-level karatekas. Moreover, it has been reported that karate performance relies more on muscle power at lower loads rather than higher ones. Thus, karate's decisive actions are essentially dependent on muscle explosive power in both the upper and lower limbs. With regard to dynamic strength, limited research has been conducted. The maximal absolute bench press, half-squat one-repetition maximum and performance of isokinetic tasks differed significantly between highly competitive and novice male karatekas. Studies on female karate athletes do not exist. Concerning flexibility, which is important for the execution of high kicks and adequate range of action at high speeds, it has been demonstrated that karate athletes' ranges of bilateral hip and knee flexion are greater compared with non-karate athletes. Finally, reaction time is a crucial element in karate because high-level performance is based essentially on explosive techniques. A significant difference in the choice reaction time between high-level and novice karatekas exists. Further research is needed concerning the physiological characteristics of female karatekas, the differences between kata and kumite athletes and variations based on weight categories.

Brain insulin action regulates eating behavior and energy fluxes throughout the body. However, numerous people are brain insulin resistant. How brain insulin responsiveness affects long-term weight and body fat composition in humans is still unknown. Here we show that high brain insulin sensitivity before lifestyle intervention associates with a more pronounced reduction in total and visceral fat during the program. High brain insulin sensitivity is also associated with less regain of fat mass during a nine year follow-up. Cross-sectionally, strong insulin responsiveness of the hypothalamus associates with less visceral fat, while subcutaneous fat is unrelated. Our results demonstrate that high brain insulin sensitivity is linked to weight loss during lifestyle intervention and associates with a favorable body fat distribution. Since visceral fat is strongly linked to diabetes, cardiovascular risk and cancer, these findings have implications beyond metabolic diseases and indicate the necessity of strategies to resolve brain insulin resistance. Brain insulin action regulates eating behavior and whole-body energy fluxes, however the impact of brain insulin resistance on long-term weight and body fat composition is unknown. Here, the authors show that high brain insulin sensitivity is linked to weight loss during lifestyle intervention and associates with a favorable body fat distribution.

Proteins are effector molecules that mediate the functions of genes1,2 and modulate comorbidities3–10, behaviors and drug treatments11. They represent an enormous potential resource for personalized, systemic and data-driven diagnosis, prevention, monitoring and treatment. However, the concept of using plasma proteins for individualized health assessment across many health conditions simultaneously has not been tested. Here, we show that plasma protein expression patterns strongly encode for multiple different health states, future disease risks and lifestyle behaviors. We developed and validated protein-phenotype models for 11 different health indicators: liver fat, kidney filtration, percentage body fat, visceral fat mass, lean body mass, cardiopulmonary fitness, physical activity, alcohol consumption, cigarette smoking, diabetes risk and primary cardiovascular event risk. The analyses were prospectively planned, documented and executed at scale on archived samples and clinical data, with a total of ~85 million protein measurements in 16,894 participants. Our proof-of-concept study demonstrates that protein expression patterns reliably encode for many different health issues, and that large-scale protein scanning12–16 coupled with machine learning is viable for the development and future simultaneous delivery of multiple measures of health. We anticipate that, with further validation and the addition of more protein-phenotype models, this approach could enable a single-source, individualized so-called liquid health check.

Abstract There is growing evidence that oxytocin (OXT), a hypothalamic hormone well recognized for its effects in inducing parturition and lactation, has important metabolic effects in both sexes. The purpose of this review is to summarize the physiologic effects of OXT on metabolism and to explore its therapeutic potential for metabolic disorders. In model systems, OXT promotes weight loss by decreasing energy intake. Pair-feeding studies suggest that OXT-induced weight loss may also be partly due to increased energy expenditure and/or lipolysis. In humans, OXT appears to modulate both homeostatic and reward-driven food intake, although the observed response depends on nutrient milieu (eg, obese vs. nonobese), clinical characteristics (eg, sex), and experimental paradigm. In animal models, OXT is anabolic to muscle and bone, which is consistent with OXT-induced weight loss occurring primarily via fat loss. In some human observational studies, circulating OXT concentrations are also positively associated with lean mass and bone mineral density. The impact of exogenous OXT on human obesity is the focus of ongoing investigation. Future randomized, placebo-controlled clinical trials in humans should include rigorous, standardized, and detailed assessments of adherence, adverse effects, pharmacokinetics/pharmacodynamics, and efficacy in the diverse populations that may benefit from OXT, in particular those in whom hypothalamic OXT signaling may be abnormal or impaired (eg, individuals with Sim1 deficiency, Prader–Willi syndrome, or craniopharyngioma). Future studies will also have the opportunity to investigate the characteristics of new OXT mimetic peptides and the obligation to consider long-term effects, especially when OXT is given to children and adolescents. (Endocrine Reviews XX: XX – XX, 2020) Graphical Abstract Graphical Abstract