The dramatic rise in health care and economic costs as well as increases in morbidity and mortality related to lifestyle behaviors and non-communicable diseases have resulted in an increasing emphasis on research and intervention initiatives aimed at primary prevention. As there is growing evidence that the antecedents of adult diseases such as obesity and osteoporosis have roots in early childhood, physical activity interventions in early childhood (4 to 6 years of age), which has been identified as a critical period, may influence the development of fat and bone mass at this young age and have a potential impact on adolescent and young adult health status and thus improve population health. The intent of this study was to investigate the effects of structured physical activity, specifically early involvement in gymnastics, on early childhood body composition development.<P>Sixty three (25 male and 38 female) 4 to 6 year old children participating in gymnastics programs were compared to 95 control (49 male and 46 female) children. Anthropometric measurements included height, weight, BMI, waist circumference, and skinfold thickness. Dual energy x-ray absorptiometry (DXA) was used to measure whole body bone density and fat mass. Physical activity, physical inactivity, dietary intake, and birth weight of the participants as well as parental heights and weights were also obtained. <P>No significant differences were found, at any age, between the groups in height, weight, BMI, waist circumference, skinfold thickness, physical activity, physical inactivity, dietary intakes, and birth weight or in parental heights and weights (p>0.05). Additionally, there were no significant differences in fat and bone parameters once the confounders of age and size were controlled (p>0.05). <P>This investigation found that young children entering a gymnastics program did not differ in either bone mass or fat mass compared to controls. This was surprising as differences in these parameters have been found in adolescent gymnasts. Thus my results indicate that the potential effects of gymnastics training may have not yet manifested themselves. To answer this question longitudinal measures are required to ascertain whether the body composition differences observed in adolescent gymnasts are due to prolonged exposure to gymnastics involvement.

Early life factors such as birth weight have been associated with the risk of disease in adulthood, including osteoporosis. In the United States, an estimated eight million women have osteoporosis, a disease characterized by low bone mass and associated with increased risk of fracture. Peak bone mass, achieved during early adulthood, is a key determinant of risk of subsequent osteoporosis. Prior studies have suggested that an individual's birth weight is positively associated with bone mineral content (BMC) and bone mineral density (BMD) but results have differed depending on site of bone measurement and other factors considered. We assessed the relationship between birth weight and BMC and BMD using data from the University of Massachusetts Vitamin D Status Study, a cross-sectional study of 186 US women aged 18 to 30 years. Birth weight was assessed via self report and BMC and BMD were measured by dual energy x-ray absorptiometry (DXA). Multivariable linear regression and multivariable logistic regression were used to model the association between birth weight and BMC and BMD, adjusting for established risk factors for low bone density. After controlling for important factors, birth weight was positively associated with BMC and BMD, in large part due to the strong relationship between birth weight and body size. A better understanding of the physiology of the association between birth weight and adult body size and peak bone mass is needed to determine if birth weight is independently associated with peak bone mass.

Origin of renal osteodystrophy and cardiovascular complications are multifactorial. This complications are caused by disorders of calcium - phosphate metabolism already at the beginning of patient's irreversible renal failure. The factors playing the most important part in the development o renal ostedystrophy and are hypocalcemia and increasing serum phosphate levels associated with a declining glomerulal filtration. Two main types of renal osteodystrophy can be described - high turnover bone disease and low turnover disease. High turnover forms of renal osteodystrophy are characterized by rapid bone turnover caused by abnormally high PTH levels. The two types of high turnover renal osteodystrophy are predominant hyperparathyroid bone disease, and mixed uremic osteodystrophy. Low turnover forms of renal osteodystrophy are characterized by a dramatic drop in the rate of bone remodeling, caused by oversuppression of PTH and/or by aluminum accumulation. The bones become thin and overly flexible, and bowing may occur. The two types of low turnover renal osteodystrophy are low turnover uremic osteodystrophy and aluminum-related bone disease. Patients who have end-stage renal disease with increased serum phosphate levels and calciumphosphate products are associated with an increased prevalence of ectopic...

Bone mineral content (BMC) and bone mineral density (BMD), measured by dual x-ray absorptiometry are used clinically to diagnose osteoporosis and estimate risk for fragility fractures. Bone mineral explains up to 70% of bone strength; however, it does not take into account bone geometry. Mechanical Response Tissue Analysis is a method of non-invasively measuring the bending stiffness (EI) of bone which is determined by the product of Young's modulus of elasticity (E) and the areal cross sectional moment of inertia (I). The aim of the current study was to determine if high intensity strength training will increase ulnar bending stiffness in young women. Forty-nine women aged 19.9 ± 1.7 yrs, trained their nondominant arm either concentrically or eccentrically in the Isokinetic modality on the Biodex® system III 3d/wk for 32 wks. The dominant arm served as the control limb (untrained). Analysis of all subjects regardless of training mode demonstrated a significant increase in ulnar EI (22% ↑, P=0.01) with no significant difference in the untrained arm. When EI results were assessed by training mode, subjects who trained eccentrically showed a significant increase for ulnar EI in the trained limb (40% ↑, P=0.01) with no significant effect on the untrained limb while concentric training demonstrated no significant gain in either the trained or untrained arm. There was no effect of time x mode of training interaction for either the trained or untrained limb. Bone mineral density and bone mineral content of the ulna increased significantly in the trained arm in both concentric and eccentric training modes (P<0.05). These findings suggest support for the hypothesis that a critical threshold of mechanical bending loads may be necessary to effect an adaptation in bone strength and thus, eccentric training may be a novel approach to increase ulnar EI in young women. / Master of Science

High body weight seems protective of bone mass, specifically bone mineral content (BMC) and bone mineral density (BMD), thereby reducing the risk of osteoporosis. Cognitive eating restraint (CER), diet composition, and the satiety hormone, leptin, produced by adipocytes, are associated with body mass and may also influence bone mass. Few studies have examined these relationships. To investigate the relationship between leptin and CER score, 36 premenopausal, healthy weight women, as defined by body mass index (BMI) of 18-25 kg/m², aged 18-25 years were studied. Women were categorized by baseline Eating Inventory questionnaire scores into either the high CER group (score > 9, n = 20) or low CER group (score < 9, n = 16). Serum leptin concentration was significantly lower in the low CER group versus high CER group at baseline. A positive relationship between serum leptin concentration and body fat mass and body fat % in normal weight women despite differences in CER scores was observed. In a separate study, overweight and obese women, (BMI > 25 to < 43 kg/m²), aged 32-45 years, were randomly assigned to either a low-carbohydrate, high-protein (LCHP) or low-fat, high-carbohydrate (LFHC) diet for 12 weeks. Serum leptin concentration was significantly greater in the LCHP versus the LFHC diet group at 12 weeks (p < 0.05). Over time, significant decreases in serum leptin concentration, BMI, body weight, total lean mass, total fat mass, and body fat % were observed in both diet groups. Serum leptin concentration was positively associated with body weight, fat mass, and body fat % regardless of diet consumed. Both studies are novel in their respective populations and show no direct link between leptin and bone mass when considered in the context of CER or diet composition. / Master of Science

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / Previous studies suggest that dietary patterns that promote acidosis may have a negative effect on bone density, whereas a more alkaline‐based profile would be associated with better bone health. Thus, the aim of this study was to assess, in omnivores, vegetarians, and vegans bone mineral density using Dual‐energy X‐ray absorptiometry (DEXA) and compare it to their acid‐base status as indicated by urinary pH, Potential Renal Acid Load (PRAL) and serum anion gap. Our hypothesis was that plant‐based diets would be associated with a more alkaline acid‐base profile than omnivorous diets, and thus have a higher bone mineral density. Methods: We conducted a cross‐sectional study where we compared plant based vs. omnivorous diets. Eighty‐two subjects were enrolled in the study (27 omnivores, 27 vegetarians, and 28 vegans). Subjects were asked to fill out a medical history form and a 24‐ hour diet recall, and to complete a 24‐hour urine collection. After a few weeks, subjects returned to the test site to complete a DEXA scan. Acid base‐balance and bone health were determined using PRAL, urine pH, and anion gap as biomarkers for pH, and DEXA as an indicator of bone density. Our results showed that bone mineral density did not differ significantly between groups, although lacto‐ovo and vegan diets were more alkaline compared to meat based diets (6.5  0.4, 6.7  0.4, and 6.2  0.4 pH respectively, p = 0.003). Protein intake was found to be reduced by ~30% in individuals adhering to a lacto‐ovarian or vegan diet; yet protein was only associated with bone mineral density in those following vegan diets. Conversely, urinary pH was associated with bone mineral density only in those following a meat‐based diet. The significance of this study is that it provides knowledge in the area of osteoporosis prevention and perhaps specific recommendations based on diet groups: increased fruit and vegetable intake for those with high meat consumption, to improve the acid‐base homeostasis, and increased plant protein intake for individuals who follow a plant-based diet.

BACKGROUND:Laxatives are among the most widely used over-the-counter medications in the United States but studies examining their potential hazardous side effects are sparse. Associations between laxative use and risk for fractures and change in bone mineral density BMD] have not previously been investigated.METHODS:This prospective analysis included 161,808 postmenopausal women (8907 users and 151,497 nonusers of laxatives) enrolled in the WHI Observational Study and Clinical Trials. Women were recruited from October 1, 1993, to December 31, 1998, at 40 clinical centers in the United States and were eligible if they were 50 to 79 years old and were postmenopausal at the time of enrollment. Medication inventories were obtained during in-person interviews at baseline and at the 3-year follow-up visit on everyone. Data on self-reported falls (greater than or equal to]2), fractures (hip and total fractures) were used. BMD was determined at baseline and year 3 at 3 of the 40 clinical centers of the WHI.RESULTS:Age-adjusted rates of hip fractures and total fractures, but not for falls were similar between laxative users and non-users regardless of duration of laxative use. The multivariate-adjusted hazard ratios for any laxative use were 1.06 (95% confidence interval CI], 1.03-1.10) for falls, 1.02 (95% CI, 0.85-1.22) for hip fractures and 1.01 (95% CI, 0.96-1.07) for total fractures. The BMD levels did not statistically differ between laxative users and nonusers at any skeletal site after 3-years intake.CONCLUSION:These findings support a modest association between laxative use and increase in the risk of falls but not for fractures. Its use did not decrease bone mineral density levels in postmenopausal women. Maintaining physical functioning, and providing adequate treatment of comorbidities that predispose individuals for falls should be considered as first measures to avoid potential negative consequences associated with laxative use.

This dissertation’s three studies investigated the short and long-term relationships of bone-related nutrient intakes with bone mineral density (BMD) in postmenopausal women. This dissertation compared the equivalency of dietary intakes assessed by eight days of diet records (DR) and the Arizona Food Frequency Questionnaire (AFFQ) at one year. It also determined the association of one year (DR) and the average of four-year (AFFQ) dietary intakes with cross-sectional BMD. The dietary intake associations with BMD were further investigated by hormone therapy (HT). Participant’s BMD was measured at the lumbar spine (L2-L4), femur trochanter, femur neck, Ward's triangle and total body using dual energy X-ray absorptiometry. Separate multiple linear regression analysis (p≤0.05), controlled for various covariates, were used to examine the associations between dietary intakes and regional and total body BMD. In study number one (n=266), significant correlations (r=0.30-0.70, p≤0.05) between dietary assessment methods were found with all dietary intake variables. Iron, magnesium, zinc, dietary calcium, phosphorous, potassium, total calcium, and fiber intakes were positively associated with BMD at three or more of the same bone sites regardless of the dietary assessment method at one year. In study number two (n=266), femur trochanter, lumbar spine, and total body BMD had mostly significant inverse associations with dietary polyunsaturated fatty acid (PUFA) intake at one year. In the HT group (n=136), inverse associations with dietary PUFA intake were seen in the spine and total body BMD. In study number three (n=130), average dietary intake of selected bone-related nutrients, were significantly inversely associated with lumbar spine BMD and total body BMD at year four. In the HT group (n=92), inverse associations with dietary PUFA intake were seen in the spine and total body BMD. The DR and AFFQ are acceptable dietary tools used to determine the associations of particular nutrients and BMD sites in healthy postmenopausal women at one year. At one and four year, dietary PUFA intakes had mostly inverse associations with lumbar spine and total body BMD. When categorized by HT use the associations remained significant only in the HT groups, suggesting that HT may influence dietary intake associations with BMD.

No description available.

Background: Daily nutrient/energy intakes are typically evaluated as a total 24-hour intake rather than as the amounts consumed per eating opportunity. Evidence suggests that smaller, frequent meals containing persistent levels of energy and protein may be more beneficial for achieving a lower body fat and higher fat-free mass than equal intakes consumed in larger and less frequent amounts. This may be due to a better-maintained energy balance (EB) that is achieved with smaller and more frequent intakes. Objective: The objective of this study was to determine the relationship between hourly EB and protein intake with body composition. Methods: Using a software program that provides hourly and 24-hour energy and nutrient intakes and hourly energy expenditures, a secondary analysis of previously collected 3-day food diaries was used to examine the relationship between hourly EB and body composition. The food and activity diaries provided information on time of food/beverage consumption and hourly energy expenditure, enabling an hourly analysis of EB. Body composition, including fat mass, fat-free mass, and bone density were examined via dual-energy x-ray absorptiometry. SPSS was used for statistical analysis, and included descriptive statistics, correlational analyses, t-tests, and regression analyses. Results: Existing data from elite female gymnasts (N=40) were assessed using an IRB-approved protocol. Higher protein consumption was significantly associated with lower bone mineral density (BMD) in the gymnasts at the arms (r= -0.535; p< 0.001), legs (r= 0.0523; p= 0.001), trunk(r= -0.517; p=0.001), spine (r= -0.472; p=0.002), and pelvis (r= -0.539; p< 0.001). Other dietary factors assessing energy and protein intakes were not significantly associated with body composition. The assessed gymnasts spent the majority of the day in hourly energy balance deficits exceeding -400 kcal. A t-test comparing subjects with higher (n=22) vs. lower (n=18) fat-free mass (FFM), using the statistical mean as the cut point, found that higher protein intakes were significantly associated with lower FFM (p=.007). Subjects with more hours spent in an EB surplus had significantly higher FFM/kg (p=.008) and lower body fat % (p=.008). Conclusion: These findings suggest that higher protein intakes may compromise BMD, a finding likely exacerbated by the long periods of time spent in EB deficits. More hours in an EB surplus was associated with positive outcomes, including higher FFM/kg and lower body fat percent. These data suggest that higher protein intakes may be consumed by gymnasts with the greatest EB deficits, perhaps as a way of minimizing (unsuccessfully) weight and fat-mass. As virtually all hours of the assessed groups were in an EB deficit, it is possible that consumed protein was used to satisfy energy needs rather than being used anabolically to support or enlarge the muscle mass. Future studies should consider addressing this issue, perhaps by assessing more heterogeneous groups where at least a proportion of the population sustains a reasonably good EB during the assessment period.