PubMed · 5324949
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B François. 1966. [Methods and reference networks in body composition].. https://pubmed.ncbi.nlm.nih.gov/5324949/
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An industrial prompt-gamma neutron activation analysis (PGNAA) system, originally designed for the real-time elemental analyses of bulk coal on a conveyor belt, has been studied to examine the feasibility of using such a system for body composition analysis. Experiments were conducted to measure nitrogen in a simple, tissue equivalent phantom comprised of 2.7 wt% of nitrogen. The neutron source for these experiments was 365 MBq (18.38 microg) of 252Cf located within an engineered low Z moderator and it yielded a dose rate in the measurement position of 3.91 mSv/h; data were collected using a 2780 cm(3) NaI(Tl) cylindrical detector with a digital signal processor and a 512 channel MCA. Source, moderator and detector geometries were unaltered from the system's standard configuration, where they have been optimized for considerations such as neutron thermalization, measurement sensitivity and uniformity, background radiation and external dose minimization. Based on net counts in the 10.8 MeV PGNAA nitrogen photopeak and its escape peaks the dose dependent nitrogen count rate was 11,600 counts/mSv with an uncertainty of 3.0% after 0.32 mSv (4.9 min), 2.0% after 0.74 mSv (11.4 min) and 1.0% after 3.02 mSv (46.4 min).
OBJECTIVE: To compare the relationship between fasting serum leptin levels and body mass index (BMI) in children from different ethnic groups. SUBJECTS: Children aged 6-10 y from rural Gambia (n=471) and central Italy (n=839). MEASUREMENTS: Anthropometry (z-score of BMI) and fasting serum leptin concentrations. RESULTS: The Italian children had significantly higher mean BMI z-scores than the Gambian children (males: Italy 1.58, Gambia -1.44, P< or =0.0001; females: Italy 1.33, Gambia -1.42, P< or =0.0001) and significantly higher serum leptin concentrations (males: Italy 8.86 ng ml(-1), Gambia 1.78 ng ml(-1), P< or =0.0001; females: Italy 11.31 ng ml(-1), Gambia 2.22 ng ml(-1), P< or =0.0001). A significantly different relationship was observed between z-score of BMI and serum leptin levels in the Gambian and the Italian children for both boys and girls. CONCLUSION: A different relationship exists between z-score of BMI and leptin levels in these two groups of children from very diverse ethnic backgrounds. Future studies using detailed measures of body composition and energy balance are needed to help understand this relationship.
Many athletes, especially female athletes and participants in endurance and aesthetic sports and sports with weight classes, are chronically energy deficient. This energy deficiency impairs performance, growth and health. Reproductive disorders in female athletes are caused by low energy availability (defined as dietary energy intake minus exercise energy expenditure), perhaps specifically by low carbohydrate availability, and not by the stress of exercise. These reproductive disorders can be prevented or reversed by dietary supplementation in compensation for exercise energy expenditure without any moderation of the exercise regimen. Energy balance is not the objective of athletic training. To maximize performance, athletes strive to achieve an optimum sport-specific body size, body composition and mix of energy stores. To pursue these objectives, athletes need to manage fat, protein and carbohydrate balances separately, but it is impractical for athletes to monitor these balances directly, and appetite is not a reliable indicator of their energy and macronutrient needs. To guide their progress, athletes need to eat by discipline and to monitor specific, reliable and practical biomarkers of their objectives. Skinfolds and urinary ketones may be the best biomarkers of fat stores and carbohydrate deficiency, respectively. Research is needed to identify and validate these and other markers.