Machine Learning Identifies Stool pH as a Predictor of Bone Mineral Density in Healthy Multiethnic US Adults.

BACKGROUND: A variety of modifiable and nonmodifiable factors such as ethnicity, age, and diet have been shown to influence bone health. Previous studies are usually limited to analyses focused on the association of a few a priori variables or on a specific subset of the population. OBJECTIVE: Dietary, physiological, and lifestyle data were used to identify directly modifiable and nonmodifiable variables predictive of bone mineral content (BMC) and bone mineral density (BMD) in healthy US men and women using machine-learning models. METHODS: Ridge, lasso, elastic net, and random forest models were used to predict whole-body, femoral neck, and spine BMC and BMD in healthy US men and women ages 18-66 y, with a BMI (kg/m2) of 18-44 (n = 313), using nonmodifiable anthropometric, physiological, and demographic variables; directly modifiable lifestyle (physical activity, tobacco use) and dietary (via FFQ) variables; and variables approximating directly modifiable behavior (circulating 25-hydroxycholecalciferol and stool pH). RESULTS: Machine-learning models using nonmodifiable variables explained more variation in BMC and BMD (highest R2 = 0.75) compared with when using only directly modifiable variables (highest R2 = 0.11). Machine-learning models had better performance compared with multivariate linear regression, which had lower predictive value (highest R2 = 0.06) when using directly modifiable variables only. BMI, body fat percentage, height, and menstruation history were predictors of BMC and BMD. For directly modifiable features, betaine, cholesterol, hydroxyproline, menaquinone-4, dihydrophylloquinone, eggs, cheese, cured meat, refined grains, fruit juice, and alcohol consumption were predictors of BMC and BMD. Low stool pH, a proxy for fermentable fiber intake, was also predictive of higher BMC and BMD. CONCLUSIONS: Modifiable factors, such as diet, explained less variation in the data compared with nonmodifiable factors, such as age, sex, and ethnicity, in healthy US men and women. Low stool pH predicted higher BMC and BMD. This trial was registered at www.clinicaltrials.gov as NCT02367287.

Weight Loss, but Not Dairy Composition of Diet, Moderately Affects Satiety and Postprandial Gut Hormone Patterns in Adults.

BACKGROUND: Inclusion of dairy in diet patterns has been shown to have mixed effects on weight loss. A prevailing hypothesis is that dairy improves weight loss by influencing endocrine systems associated with satiety and food intake regulation. OBJECTIVES: The objective of the current study was to evaluate the effect of weight loss with or without adequate dietary dairy on subjective and objective appetitive measures. METHODS: Men and women who were habitual low dairy consumers (n = 65, 20-50 y) participated in a 12-wk randomized controlled feeding weight loss trial. During the 12-wk intervention, a low-dairy (<1 serving dairy/d) was compared with an adequate-dairy (3-4 servings dairy/d) diet, both with a 500-kcal deficit/d. Test days, before and at the end of the intervention, began with 2 fasting blood draws and visual analog scale (VAS) measures, followed by a standard breakfast (25% of prescribed restricted calories), 5 postbreakfast blood draws and VASs, a standard lunch (40% of restricted energy amount), and 12 postlunch blood draws and VASs. Blood samples were used for satiety hormone measurements. On a separate day when matching standard meals were consumed, an ad libitum buffet meal was provided as dinner, at a self-selected time. Meal duration and intermeal interval were recorded. RESULTS: Weight loss (-6.1 kg), irrespective of dairy, resulted in reduced fasting insulin (-20%) and leptin (-25%), and increased fasting acylated ghrelin (+25%) and VAS desire to eat (+18%) (P < 0.05). There were no effects of dairy on objective or subjective satiety measures. Weight loss marginally reduced the intermeal interval (289 min compared with 276 min, P = 0.059) between lunch and the ad libitum buffet. CONCLUSIONS: These results do not support the hypothesis that inclusion of dairy in long-term dietary patterns influences appetite during weight loss. Weight loss per se has a modest impact on select systems that regulate hunger and satiety.This trial was registered at clinicaltrials.gov as NCT00858312.

Disordered Eating, Development of Menstrual Irregularity, and Reduced Bone Mass Change After a 3-Year Follow-Up In Female Adolescent Endurance Runners.

This prospective study evaluated the 3-year change in menstrual function and bone mass among 40 female adolescent endurance runners (age 15.9 ± 1.0 years) according to baseline disordered eating status. Three years after initial data collection, runners underwent follow-up measures including the Eating Disorder Examination Questionnaire and a survey evaluating menstrual function, running training, injury history, and prior sports participation. Dual-energy X-ray absorptiometry was used to measure bone mineral density and body composition. Runners with a weight concern, shape concern, or global score ≥4.0 or reporting >1 pathologic behavior in the past 28 days were classified with disordered eating. Compared with runners with normal Eating Disorder Examination Questionnaire scores at baseline, runners with disordered eating at baseline reported fewer menstrual cycles/year (6.4 ± 4.5 vs. 10.5 ± 2.8, p = .005), more years of amenorrhea (1.6 ± 1.4 vs. 0.3 ± 0.5, p = .03), and a higher proportion of menstrual irregularity (75.0% vs. 31.3%, p = .02) and failed to increase lumbar spine or total hip bone mineral density at the 3-year follow-up. In a multivariate model including body mass index and menstrual cycles in the past year at baseline, baseline shape concern score (B = -0.57, p value = .001) was inversely related to the annual number of menstrual cycles between assessments. Weight concern score (B = -0.40, p value = .005) was inversely associated with lumbar spine bone mineral density Z-score change between assessments according to a multivariate model adjusting for age and body mass index. These finding support associations between disordered eating at baseline and future menstrual irregularities or reduced accrual of lumbar spine bone mass in female adolescent endurance runners.

Vitamin D3 Supplementation Increases Spine Bone Mineral Density in Adolescents and Young Adults With Human Immunodeficiency Virus Infection Being Treated With Tenofovir Disoproxil Fumarate: A Randomized, Placebo-Controlled Trial.

Background: Tenofovir disoproxil fumarate (TDF) decreases bone mineral density (BMD). We hypothesized that vitamin D3 (VITD3) would increase BMD in youth receiving TDF. Methods: This was a randomized, double-blind, placebo-controlled trial of directly observed VITD3 vs placebo every 4 weeks for 48 weeks in youth aged 16-24 years with HIV, RNA load <200 copies/mL, taking TDF-containing combination antiretroviral therapy (TDF-cART) for ≥180 days. Participants (N = 214) received a daily multivitamin containing VITD3 400 IU and calcium 162 mg, plus monthly randomized VITD3 50000 IU (n = 109) or placebo (n = 105). Outcome was change from baseline to week 48 in lumbar spine BMD (LSBMD). Data presented are median (Q1, Q3). Results: Participants were aged 22.0 (21.0, 23.0) years, 84% were male, and 74% were black/African American. At baseline, 62% had 25-hydroxy vitamin D (25-OHD) <20 ng/mL. Multivitamin adherence was 49% (29%, 69%), and VITD3/placebo adherence 100% (100%, 100%). Vitamin D intake was 2020 (1914, 2168) and 284 (179, 394) IU/day, and serum 25-OHD concentration was 36.9 (30.5, 42.4) and 20.6 (14.4, 25.8) ng/mL at 48 weeks in VITD3 and placebo groups, respectively (P < .001). From baseline to week 48, LSBMD increased by 1.15% (-0.75% to 2.74%) in the VITD3 group (n = 99; P < .001) and 0.09% (-1.49% to 2.61%) in the placebo group (n = 89; P = .25), without between-group difference (P = .12). VITD3 group changes occurred with baseline 25-OHD <20 ng/mL (1.17% [-.82% to 2.90%]; P = .004) and ≥20 ng/mL (0.93% [-.26% to 2.15%]; P = .033). Conclusions: For youth taking TDF-cART, LSBMD increased through 48 weeks with VITD3 plus multivitamin, but not with placebo plus multivitamin, independent of baseline vitamin D status. Clinical Trials Registration: NCT01751646.

Decline in Bone Mass With Tenofovir Disoproxil Fumarate/Emtricitabine Is Associated With Hormonal Changes in the Absence of Renal Impairment When Used by HIV-Uninfected Adolescent Boys and Young Men for HIV Preexposure Prophylaxis.

BACKGROUND: We aimed to define the relative importance of renal and endocrine changes in tenofovir disoproxil fumarate (TDF)-related bone toxicity. METHODS: In a study of daily TDF/emtricitabine (FTC) preexposure prophylaxis (PrEP) in human immunodeficiency virus (HIV)-uninfected young men who have sex with men, we measured changes from baseline in blood and urine markers of the parathyroid hormone (PTH)-vitamin D-fibroblast growth factor 23 (FGF23) axis, creatinine, and renal tubular reabsorption of phosphate (TRP). We explored the relationship of those variables to changes in bone mineral density (BMD). Tenofovir-diphosphate (TFV-DP) in red blood cells was used to categorize participants into high and low drug exposure groups. RESULTS: There were 101 participants, median age 20 years (range 15 to 22). Compared with low drug exposure, high-exposure participants showed increase from baseline in PTH and decline in FGF23 by study week 4, with no differences in creatinine, phosphate, or TRP. At 48 weeks, the median (interquartile range) percent decline in total hip BMD was greater in those with high- compared to low- exposure (-1.59 [2.77] vs +1.54 [3.34] %, respectively; P = .001); in high-exposure participants, this correlated with week 4 TFV-DP (inversely; r = -0.60, P = .002) and FGF23 (directly; r = 0.42; P = .039) but not other variables. CONCLUSIONS: These findings support the short-term renal safety of TDF/FTC PrEP in HIV-seronegative young men and suggest that endocrine disruption (PTH-FGF23) is a primary contributor to TDF-associated BMD decline in this age group. CLINICAL TRIALS REGISTRATION: NCT01769469.

Habitual physical activity and plasma metabolomic patterns distinguish individuals with low vs. high weight loss during controlled energy restriction.

BACKGROUND: Total weight loss induced by energy restriction is highly variable even under tightly controlled conditions. Identifying weight-loss discriminants would provide a valuable weight management tool and insights into body weight regulation. OBJECTIVE: This study characterized responsiveness to energy restriction in adults from variables including the plasma metabolome, endocrine and inflammatory markers, clinical indices, body composition, diet, and physical activity. METHODS: Data were derived from a controlled feeding trial investigating the effect of 3-4 dairy product servings in an energy-restricted diet (2092 kJ/d reduction) over 12 wk. Partial least squares regression was used to identify weight-loss discriminants in 67 overweight and obese adults. Linear mixed models were developed to identify discriminant variable differences in high- vs. low-weight-loss responders. RESULTS: Both pre- and postintervention variables (n = 127) were identified as weight-loss discriminants (root mean squared error of prediction = 1.85 kg; Q(2) = 0.43). Compared with low-responders (LR), high-responders (HR) had greater decreases in body weight (LR: 2.7 ± 1.6 kg; HR: 9.4 ± 1.8 kg, P < 0.01), BMI (in kg/m(2); LR: 1.0 ± 0.6; HR: 3.3 ± 0.5, P < 0.01), and total fat (LR: 2.2 ± 1.1 kg; HR: 8.0 ± 2.1 kg, P < 0.01). Significant group effects unaffected by the intervention were determined for the respiratory exchange ratio (LR: 0.86 ± 0.05; HR: 0.82 ± 0.03, P < 0.01), moderate physical activity (LR: 127 ± 52 min; HR: 167 ± 68 min, P = 0.02), sedentary activity (LR: 1090 ± 99 min; HR: 1017 ± 110 min, P = 0.02), and plasma stearate [LR: 102,000 ± 21,000 quantifier ion peak height (QIPH); HR: 116,000 ± 24,000 QIPH, P = 0.01]. CONCLUSIONS: Overweight and obese individuals highly responsive to energy restriction had accelerated reductions in adiposity, likely supported in part by higher lipid mobilization and combustion. A novel observation was that person-to-person differences in habitual physical activity and magnitude of weight loss were accompanied by unique blood metabolite signatures. This trial was registered at clinicaltrials.gov as NCT00858312.

A feasibility study of wearable activity monitors for pre-adolescent school-age children.

INTRODUCTION: Understanding physical activity is key in the fight against childhood obesity. The objective of this study was to examine the feasibility of using certain wearable devices to measure physical activity among children. METHODS: A qualitative study was conducted with 25 children aged 7 to 10 years to assess acceptability and compliance of wearable activity devices in this age group. During March through August 2012, children participated in a 4-week study of 3 accelerometer models and a heart rate monitor. Children were asked to use a different device each week for 7 consecutive days. Children and their parents completed structured interviews after using each device; they also completed a final exit interview. RESULTS: The wrist-worn Polar Active was the device most preferred by children and was associated with the highest level of compliance. Devices that are comfortable to wear, fit properly, have engaging features, and are waterproof increase feasibility and are associated with higher levels of compliance. CONCLUSION: The wrist-worn device was the most feasible for measuring physical activity among children aged 7 to 10 years. These findings will inform researchers in selecting tools for measuring children's physical activity.

Bone Biomarkers and Subsequent Survival in Men with Hormone-sensitive Prostate Cancer: Results from the SWOG S1216 Phase 3 Trial of Androgen Deprivation Therapy with or Without Orteronel.

BACKGROUND: Bone biomarkers are strongly prognostic for overall survival (OS) in men with castration-resistant prostate cancer but not fully established for hormone-sensitive prostate cancer (HSPC). OBJECTIVE: Bone biomarkers in HSPC were prospectively evaluated as part of a phase 3 study of androgen deprivation therapy ± the CYP17 inhibitor orteronel. DESIGN, SETTING, AND PARTICIPANTS: Patients were randomly divided into training (n = 316) and validation (n = 633) sets. Recursive partitioning and Cox proportional hazard models were employed. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Bone resorption (C-telopeptide and pyridinoline) and bone formation markers (C-terminal collagen propeptide and bone alkaline phosphatase) were assessed from patient sera. RESULTS AND LIMITATIONS: Of 1279 men, 949 had evaluable baseline bone biomarkers. Optimal cutoffs were identified to define elevated levels of each of the four biomarkers (all p < 0.05) that were associated with worse OS. After adjusting for clinical risk factors in the validation set, elevated bone biomarkers were statistically significantly associated with an increased risk of death (hazard ratios ranging from 1.37 to 1.92). Recursive partitioning algorithms applied to the training set identified three risk groups (low, intermediate, and poor) with differential OS outcomes (median OS: 8.2, 5.1, and 2.1 yr, respectively) based on combinations of bone biomarkers. These results were confirmed in the validation set. CONCLUSIONS: In men with HSPC initiating androgen deprivation therapy, bone biomarkers are strongly and independently prognostic for OS. Bone biomarker levels alone or in combination with clinical covariates identify unique subsets of men with differential OS outcomes. These results validate the clinical value of bone biomarker assessment in the HSPC state, extending bone biomarker utility beyond the castration-resistant state. PATIENT SUMMARY: In men with newly diagnosed metastatic prostate cancer, high levels of bone turnover biomarkers are associated with a shorter lifespan.

Markers of bone metabolism and overall survival in men with bone-metastatic hormone sensitive prostate cancer (HSPC): A subset analysis of SWOG S1216, a phase III trial of androgen deprivation with or without orteronel.

BACKGROUND: Circulating biomarkers of bone metabolism are significantly associated with overall survival (OS) in men with advanced prostate cancer. In the SWOG S1216 phase III trial, we showed that elevated bone biomarkers are significantly associated with an increased risk of death in hormone-sensitive prostate cancer (HSPC) regardless of the status of bone metastases, identifying three risk groups with differential OS outcomes based on bone biomarker status. Here we report the association of bone biomarkers with OS in men with HSPC and documented skeletal metastases as part of a planned subset analysis of S1216. METHODS: Bone resorption [C-telopeptide (CTx); Pyridinoline (PYD)] and bone formation markers [C-terminal collagen propeptide (CICP); bone alkaline phosphatase (BAP)] were assessed in blood from men with bone metastatic HSPC. Patients were randomly divided into training (n = 238) and validation (n = 475) sets. In the training set, recursive partitioning that maximizes discrimination of OS was used to identify the dichotomous cut-point for each biomarker and for a combination of biomarker split points to define prognostic groups. In the validation set, Cox proportional hazards models were used to assess the impact of biomarkers on OS, adjusted for patient and tumor characteristics. RESULTS: Of 1279 men, 713 had both baseline bone metastases and evaluable bone biomarkers. Patient characteristics were similar between the overall population and the subset with bone metastases. Elevated levels of CICP, CTX, and PYD were strongly prognostic for OS. Hazard ratios (95% CI) for OS adjusted for treatment arm and baseline clinical variables were: BAP-1.31 (0.93, 1.84), p = 0.12; CICP-1.58 (1.09, 2.29), p < 0.02; CTx - 1.55 (1.12, 2.15), p = 0.008; and PYD-1.66 (1.27, 2.217), p = 0.0002. There was no evidence of interaction between elevated biomarkers and treatment (all p > 0.2). Recursive partitioning algorithms identified four groups of patients with differential OS outcomes based on bone biomarkers, adjusted for baseline clinical variables, with median OS ranging from 2.3 years (highest risk group) to 7.5 years (lowest risk group). CONCLUSIONS: In this planned S1216 subset analysis of men with HSPC and bone metastases, elevated serum markers of bone metabolism were significantly associated with worse OS. Bone biomarker levels alone and in combination with patient and tumor characteristics identify unique subsets of men with differential OS outcomes. GOV IDENTIFIER: NCT01809691.

Association of higher plasma vitamin D binding protein and lower free calcitriol levels with tenofovir disoproxil fumarate use and plasma and intracellular tenofovir pharmacokinetics: cause of a functional vitamin D deficiency?

Tenofovir disoproxil fumarate (TDF) causes bone, endocrine, and renal changes by an unknown mechanism(s). Data are limited on tenofovir pharmacokinetics and these effects. Using baseline data from a multicenter study of HIV-infected youth on stable treatment with regimens containing TDF (n = 118) or lacking TDF (n = 85), we measured cross-sectional associations of TDF use with markers of renal function, vitamin D-calcium-parathyroid hormone balance, phosphate metabolism (tubular reabsorption of phosphate and fibroblast growth factor 23 [FGF23]), and bone turnover. Pharmacokinetic-pharmacodynamic associations with plasma tenofovir and intracellular tenofovir diphosphate concentrations were explored among those receiving TDF. The mean age was 20.9 (standard deviation [SD], 2.0) years; 63% were male; and 52% were African American. Compared to the no-TDF group, the TDF group showed lower mean estimated glomerular filtration rates and tubular reabsorption of phosphate, as well as higher parathyroid hormone and 1,25-dihydroxy vitamin D [1,25-OH(2)D] levels. The highest quintile of plasma tenofovir concentrations was associated with higher vitamin D binding protein, lower free 1,25-OH(2)D, higher 25-OH vitamin D, and higher serum calcium. The highest quintile of intracellular tenofovir diphosphate concentration was associated with lower FGF23. Higher plasma tenofovir concentrations were associated with higher vitamin D binding protein and lower free 1,25-OH(2)D, suggesting a functional vitamin D deficiency explaining TDF-associated increased parathyroid hormone. The finding of lower FGF23 accompanying higher intracellular tenofovir diphosphate suggests that different mechanisms mediate TDF-associated changes in phosphate handling. Separate pharmacokinetic properties may be associated with distinct TDF toxicities: tenofovir with parathyroid hormone and altered calcium balance and tenofovir diphosphate with hypophosphatemia and FGF23 regulation. (The clinical trial registration number for this study is NCT00490412 and is available online at http://clinicaltrials.gov/ct2/show/NCT00490412.).

Dairy food consumption and meal-induced cortisol response interacted to influence weight loss in overweight women undergoing a 12-week, meal-controlled, weight loss intervention.

Dairy food enhances weight loss in animal models, possibly by modifying the metabolic effects of cortisol. This study determined in overweight women (ages 20.0-45.9 y; n = 51) whether including dairy food in an energy-restricted diet affects cortisol concentrations and whether differences in provoked cortisol explain the magnitude of weight loss. Women received either an adequate amount of dairy food (AD), the equivalent of ≥711 mL/d milk, or a low amount of dairy food (LD), the equivalent to ≤238 mL/d milk, in a 12-wk, energy-restricted dietary intervention. Participants were tested in a 12-h laboratory visit, which included 2 standard meals and a dinner buffet that was consumed ad libitum. Salivary cortisol was measured from waking to bedtime. Energy restriction increased (P ≤ 0.04) the minimum and decreased (P ≤ 0.02) the diurnal amplitude in the salivary cortisol concentration from baseline to postintervention. Energy restriction enhanced the dinner meal-stimulated salivary cortisol response (DMR) (P ≤ 0.02) but only in the LD group. Compared with the LD treatment, the AD treatment induced (P ≤ 0.04) greater reductions in body weight and fat, but only in women characterized as having a baseline DMR (responders) (n = 26); weight and fat lost in the AD and LD groups were similar in nonresponders (n = 25). Overall, energy restriction dampened diurnal salivary cortisol fluctuations [symptomatic of hypothalamic-pituitary-adrenal (HPA) axis dysfunction] and enhanced dinner meal-stimulated salivary cortisol concentrations. The AD treatment prevented the latter. Furthermore, certain phenotypic markers of HPA axis function may help to expose the weight-reducing effects of consuming dairy food.

An Intervention of Four Weeks of Time-Restricted Eating (16/8) in Male Long-Distance Runners Does Not Affect Cardiometabolic Risk Factors.

Timing of nutrient intake for athletes may affect exercise performance and cardiometabolic factors. Our objective was to examine the effect of time-restricted eating (TRE) on cardiometabolic health. Using a cross-over study design, 15 endurance-trained male runners were randomized to either a normal dietary pattern (ND) first (12 h eating/fasting times) followed by time-restricted eating (TRE) pattern (16 h fast; 8 h eating) or the reverse, with a 4-week washout period between interventions. Body composition, resting energy expenditure, blood pressure and serum insulin, glucose and lipids were measured using standard laboratory methods. Exercise training and dietary intake (calories and macronutrients) were similar across interventions. No significant differences were observed in resting energy expenditure, markers of insulin resistance, serum lipids or blood pressure. Body composition did change significantly (p < 0.05) with whole body fat mass (-0.8 ± 1.3 kg with TRE vs. +0.1 ± 4.3 kg with ND), leg fat mass (-0.3 ± 0.5 kg with TRE vs. +0.1 ± 0.4 kg with ND), and percent body fat (-1.0 ± 1.5% with TRE vs. +0.1 ± 1.3% with ND) declining more in the TRE intervention, with no change in fat-free mass. This study is one of a few to investigate the effects of an isocaloric 16/8 TRE eating pattern in trained endurance athletes and confirms no change in cardiometabolic risk factors. In conclusion, TRE is not detrimental to cardiometabolic health in endurance-trained male runners but could be beneficial on exercise performance by reducing fat mass.

Vitamin D3 decreases parathyroid hormone in HIV-infected youth being treated with tenofovir: a randomized, placebo-controlled trial.

BACKGROUND: The study goal was to determine the effect of vitamin D (VITD) supplementation on tubular reabsorption of phosphate (TRP), parathyroid hormone (PTH), bone alkaline phosphatase (BAP), and C-telopeptide (CTX) in youth infected with human immunodeficiency virus (HIV) receiving and not receiving combination antiretroviral therapy (cART) containing tenofovir disoproxil fumarate (TDF). METHODS: This randomized, double-blind, placebo-controlled multicenter trial enrolled HIV-infected youth 18-25 years based on stable treatment with cART containing TDF (n = 118) or no TDF (noTDF; n = 85), and randomized within those groups to vitamin D3, 50 000 IU (n = 102) or placebo (n = 101), administered at 0, 4, and 8 weeks. Outcomes included change in TRP, PTH, BAP, and CTX from baseline to week 12 by TDF/noTDF; and VITD/placebo. RESULTS: At baseline, VITD and placebo groups were similar except those on TDF had lower TRP and higher PTH and CTX. At week 12, 95% in the VITD group had sufficient serum 25-hydroxy vitamin D (25-OHD; ≥20 ng/mL), increased from 48% at baseline, without change in placebo (P < .001). PTH decreased in the TDF group receiving VITD (P = .031) but not in the noTDF group receiving VITD, or either placebo group. The decrease in PTH with VITD in those on TDF occurred with insufficient and sufficient baseline 25-OHD (mean PTH change, -7.9 and -6.2 pg/mL; P = .031 and .053, respectively). CONCLUSIONS: In youth on TDF, vitamin D3 supplementation decreased PTH, regardless of baseline 25-OHD concentration. CLINICAL TRIALS REGISTRATION: NCT00490412.

Adolescent Endurance Runners Exhibit Suboptimal Energy Availability and Intakes of Key Nutrients.

Backgroud: Despite the evidence of an elevated prevalence of low bone mass in adolescent endurance runners, reports on dietary intake in this population is limited.Objectives: This study aimed to evaluate energy availability (EA) and dietary intake among 72 (n = 60 female, n = 12 male) high school cross-country runners.Methods: The sample consisted of a combined dataset of two cohorts. In both cohorts, the Block Food Frequency Questionnaire (FFQ; 2005 & 2014 versions) assessed dietary intake. Fat free mass was assessed using dual-energy x-ray absorptiometry or bioelectrical impedance analysis.Results: Mean EA was less than recommended (45 kcal/kgFFM/day) among male (35.8 ± 14.4 kcal/kg FFM/day) and female endurance runners (29.6 ± 17.4 kcal/kgFFM/day), with 30.0% of males and 60.0% of females meeting criteria for low EA (<30 kcal/kgFFM/day). Calorie intake for male (2,614.2 ± 861.8 kcal/day) and female (1,879.5 ± 723.6 kcal/day) endurance runners fell below the estimated energy requirement for "active" boys (>3,100 kcal/day) and girls (>2,300 kcal/day). Female endurance runners' relative carbohydrate intake (4.9 ± 2.1 g/kg/day) also fell below recommended levels (6-10 g/kg/day). Male and female endurance runners exhibited below-recommended intakes of calcium, vitamin D, potassium, fruit, vegetables, grains, and dairy. Compared to male endurance runners, female endurance runners demonstrated lower relative intakes of energy (kcal/kg/day), protein (g/kg/day), fat (g/kg/day), fiber, vegetables, total protein, and oils.Conclusion: This study provides evidence of the nutritional risk of adolescent endurance runners and underscores the importance of nutritional support efforts in this population.

The soy isoflavones for reducing bone loss study: 3-yr effects on pQCT bone mineral density and strength measures in postmenopausal women.

Soy isoflavones exert inconsistent bone density-preserving effects, but the bone strength-preserving effects in humans are unknown. Our double-blind randomized controlled trial examined 2 soy isoflavone doses (80 or 120mg/d) vs placebo tablets on volumetric bone mineral density (vBMD) and strength (by means of peripheral quantitative computed tomography) in healthy postmenopausal women (46-63yr). We measured 3-yr changes in cortical BMD (CtBMD), cortical thickness (CtThk), periosteal circumference (PC), endosteal circumference (EC), and strength-strain index (SSI) at 1/3 midshaft femur (N=171), and trabecular BMD (TbBMD), PC, and SSI at 4% distal tibia (N=162). We found no treatment effect on femur CtThk, PC, or EC, or tibia TbBMD or PC. The strongest predictors (negative) of tibia TbBMD and SSI and femur CtBMD were timepoint and bone resorption; whole-body fat mass was protective of SSI. As time since last menstrual period (TLMP) increased (p=0.012), 120-mg/d dose was protective of CtBMD. The strongest predictors of femur SSI were timepoint, bone resorption, and TLMP (protective). Isoflavone tablets were negative predictors of SSI, but 80-mg/d dose became protective as bone turnover increased (p=0.011). Soy isoflavone treatment for 3yr was modestly beneficial for midshaft femur vBMD as TLMP increased and for midshaft femur SSI as bone turnover increased.

Four Weeks of 16/8 Time Restrictive Feeding in Endurance Trained Male Runners Decreases Fat Mass, without Affecting Exercise Performance.

BACKGROUND: Time restricted Feeding (TRF) is a dietary pattern utilized by endurance athletes, but there is insufficient data regarding its effects on performance and metabolism in this population. The purpose of this investigation was to examine the effects of a 16/8 TRF dietary pattern on exercise performance in trained male endurance runners. METHODS: A 4-week randomized crossover intervention was used to compare an 8-h TRF to a 12-h normal diet (ND) feeding window. Exercise training and dietary intake were similar across interventions. Runners completed a dual-energy X-ray absorptiometry (DXA) scan to assess body composition, a graded treadmill running test to assess substrate utilization, and ran a 10 km time trial to assess performance. RESULTS: There was a significant decrease in fat mass in the TRF intervention (-0.8 ± 1.3 kg with TRF (p = 0.05), vs. +0.1 ± 4.3 kg with ND), with no significant change in fat-free mass. Exercise carbon dioxide production (VCO2) and blood lactate concentration were significantly lower with the TRF intervention (p ≤ 0.02). No significant changes were seen in exercise respiratory exchange ratio or 10 km time trial performance (-00:20 ± 3:34 min:s TRF vs. -00:36 ± 2:57 min:s ND). CONCLUSION: This investigation demonstrated that adherence to a 4-week 16/8 TRF dietary intervention decreased fat mass and maintained fat-free mass, while not affecting running performance, in trained male endurance runners.

Cognitive dietary restraint score is associated with lower energy, carbohydrate, fat, and grain intake among female adolescent endurance runners.

This cross-sectional study investigated associations between cognitive dietary restraint (CDR), energy, macronutrient and food group intake, menstrual function, and bone density in female adolescent endurance runners. Participants were forty female adolescent endurance runners. The independent variable was CDR, as assessed by the Three Factor Eating Questionnaire (TFEQ). Runners with CDR subscale scores ≥11 were classified with elevated CDR. The main outcomes measured were dietary intake measured by 24-hour recall for 7 days, menstrual history, and bone mineral density (BMD). Twelve of 40 participants (30.0%) met criteria for elevated CDR. Compared to runners with normal CDR, runners with elevated CDR scores reported consuming lower energy (kcal/kg/day) (37.5 ± 8.6 vs. 44.0 ± 9.6, p = 0.052), lower carbohydrate (g/kg/day) (5.3 ± 1.3 vs. 6.3 ± 1.3, p = 0.042), more fiber (g/day) (24.9 ± 6.7 vs. 20.0 ± 5.3, p = 0.018), more servings of fruit (3.3 ± 1.4 vs. 1.9 ± 1.2, p = 0.003), more servings of vegetables (2.7 ± 1.4 vs. 1.7 ± 0.7, p = 0.004), and fewer servings of grain (7.6 ± 2.4 vs. 9.8 ± 2.4, p = 0.009) per day. Runners with elevated CDR exhibited significantly lower lumbar spine BMD Z-scores (adjusting for BMI) (-0.78 ± 0.19 vs. -0.22 ± 0.12, p = 0.016) than runners with normal CDR. Menstrual history did not significantly differ based on CDR status. Elevated CDR may increase risk of dietary patterns associated with consuming inadequate levels of energy, key nutrients, and developing low BMD in endurance runners. Trial Registration:ClinicalTrials.gov Identifier: NCT01059968.

Can changes in body mass and total body water accurately predict hyponatremia after a 161-km running race?

OBJECTIVE: To relate changes in body mass, total body water (TBW), extracellular fluid (ECF), and serum sodium concentration ([Na]) from a 161-km ultramarathon to finish time and incidence of hyponatremia. DESIGN: Observational. SETTING: : The 2008 Rio Del Lago 100-Mile (161-km) Endurance Run in Granite Bay, California. PARTICIPANTS: Forty-five runners. MAIN OUTCOME MEASUREMENTS: Pre-race and post-race body mass, TBW, ECF, and serum [Na]. RESULTS: Body mass and serum [Na] significantly decreased 2% to 3% (P < 0.001) from pre-race to post-race, but TBW and ECF were unchanged. Significant relationships were observed between finish time and percentage change in body mass (r = 0.36; P = 0.01), TBW (r = 0.50; P = 0.007), and ECF (r = 0.61; P = 0.003). No associations were found between post-race serum [Na] and percentage change in body mass (r = -0.04; P = 0.94) or finish time (r = 0.5; P = 0.77). Hyponatremia (serum [Na] < 135 mmol/L) was present among 51.2% of finishers. Logistic regression prediction equation including pre-race TBW and percentage changes in TBW and ECF had an 87.5% concordance with the classification of hyponatremia. CONCLUSIONS: Hyponatremia occurred in over half of the 161-km ultramarathon finishers but was not predicted by change in body mass. The combination of pre-race TBW and percentage changes in TBW and ECF explained 87.5% of the variation in the incidence of hyponatremia. CLINICAL SIGNIFICANCE: Exercise-associated hyponatremia can occur simultaneously with dehydration and cannot be predicted by weight checks at races.

Lipid metabolism predicts changes in body composition during energy restriction in overweight humans.

Dietary weight loss regimens could be more effective by selectively targeting adipose while sparing lean mass (LM) if predictive information about individuals' lipid metabolic responses to an intervention were available. The objective of this study was to examine the relationships among changes in 4 anthropometric outcomes, weight, waist circumference (WC), percent body fat (BF), and percent LM, and comprehensive circulating lipid metabolites in response to energy reduction in overweight participants. This was a cohort study (n = 46) from a larger multi-center (n = 105) weight loss trial. We used stepwise regression to examine relationships among baseline plasma fatty acids of 7 lipid classes, biochemical metabolites, and diet to explain the variance of 4 anthropometric outcomes after intervention. No predictor variables explained the variance in the percent change in body weight. The circulating concentration of FFA 18:1(n-9) at baseline explained 31% of the variance in percent change of WC, with adjustment for energy intake at 12 wk. Circulating concentrations of phosphatidylcholine 18:0 and FFA 18:1(n-9) at baseline together explained 33% of the variance in percent LM change. The circulating concentration of phosphatidylcholine 18:0 at baseline explained 23% of the variance in the change in percent BF. This study determined relationships among comprehensive and quantitative measurements of complex lipid metabolites and metabolic outcomes as changes in body composition. Measurements of plasma circulating metabolites explained 20-30% of the variance in changes in body composition after a weight loss intervention. Thus, circulating lipids reflect lipid metabolism in relation to changes in body composition.

The role of dairy foods and dietary calcium in weight management.

Overweight and obesity are the foremost public health problems in the U.S., other industrialized countries, and is rapidly increasing in developing countries. Obesity is a multifaceted disease which requires multiple approaches to successfully combat its increase. Nutritional factors play a key role and include modification of energy balance, intake and expenditure, as well as other factors. Emerging scientific evidence over the past decade suggests that dairy foods may be beneficial when included in a moderate energy restricted diet and possibly for weight maintenance as well. This paper provides a review of some of the scientific evidence that has examined the effect of dairy foods and dietary calcium on weight management. Topic areas presented are observational or retrospective studies with adults as well as children and adolescents; randomized clinical trials on body weight and composition, energy expenditure, substrate oxidation and fecal fat loss; research from animal and in vitro studies provide possible mechanisms of action.