OBJECTIVE:Assess the utility of peripheral quantitative computed tomography (pQCT) for estimating whole body fat in adolescent girls.RESEARCH METHODS AND PROCEDURES:Our sample included 458 girls (aged 10.7 ± 1.1y, mean BMI = 18.5 ± 3.3 kg/m2) who had DXA scans for whole body percent fat (DXA %Fat). Soft tissue analysis of pQCT scans provided thigh and calf subcutaneous percent fat and thigh and calf muscle density (muscle fat content surrogates). Anthropometric variables included weight, height and BMI. Indices of maturity included age and maturity offset. The total sample was split into validation (VS; n = 304) and cross-validation (CS; n = 154) samples. Linear regression was used to develop prediction equations for estimating DXA %Fat from anthropometric variables and pQCT-derived soft tissue components in VS and the best prediction equation was applied to CS.RESULTS:Thigh and calf SFA %Fat were positively correlated with DXA %Fat (r = 0.84 to 0.85; p <0.001) and thigh and calf muscle densities were inversely related to DXA %Fat (r = -0.30 to -0.44; p < 0.001). The best equation for estimating %Fat included thigh and calf SFA %Fat and thigh and calf muscle density (adj. R2 = 0.90; SEE = 2.7%). Bland-Altman analysis in CS showed accurate estimates of percent fat (adj. R2 = 0.89; SEE = 2.7%) with no bias.DISCUSSION:Peripheral QCT derived indices of adiposity can be used to accurately estimate whole body percent fat in adolescent girls.

Physical activity that involves high-impact, rapid, and forceful loads is a positive skeletal modulator during growth. However, few studies of the relationship between physical activity and bone have incorporated bone-loading exposure into assessments. PURPOSE: This study aimed to quantify bone-loading exposure from physical activity and evaluate its relation to volumetric bone mineral density (vBMD), geometry, and strength (i.e. bone strength index (BSI); polar moment of inertia (PMI); strength strain index (SSI)) in young girls. METHODS: Prepubescent (PRE, n = 101) and early pubescent (EARLY, n = 225) girls aged 9-12 years completed a modified version of the past year physical activity questionnaire (PYPAQ), which was scored based on the aerobic intensity, peak strain score, frequency, and duration of each activity identified. The PYPAQ was modified to incorporate a broader range of peak strain scores (0.5-3.0) to increase the contribution of bone-loading activities to the overall score. Peripheral quantitative computed tomography (pQCT) was used to assess the 4% and 20% femur and the 4% and 66% tibia of the non-dominant leg. For each maturation group, multiple linear regression was used to compare bone outcomes with PYPAQ score and pedometer score, after adjusting for body weight, leg length, ethnicity, dietary Ca2+, and vitamin D intake. RESULTS: In PRE girls, PYPAQ score was not a significant (p > 0.05) predictor of bone outcomes. In EARLY girls, PYPAQ score independently and significantly (p < 0.05) predicted BSI, PMI, and SSI at the 4% femur and tibia sites. PYPAQ score also independently and significantly (p < 0.05) predicted cortical area, periosteal circumference, PMI, and SSI at the 20% femur and 66% tibia. Pedometer score did not significantly (p > 0.05) predict any bone outcome in PRE or EARLY girls. CONCLUSION: In EARLY girls, participation in activities that involved high peak strain rates and high-strain magnitudes was more important for predicting bone structural strength than overall physical activity level measured by pedometer. Bone-loading exposure is an important component of physical activity assessments aimed to determine the relationship between physical activity and bone. Supported by NIH Grant ROI HD050775.

Accurate prediction of weight loss success and failure has eluded researchers for many years. Thus, we administered a comprehensive psychometric battery before a 4-month lifestyle behavioral weight reduction program and analyzed weight changes during that period to identify baseline characteristics of successful and unsuccessful participants, among 112 overweight and obese middle-aged women (age, 47.8 ± 4.4 years; BMI, 31.4 ± 3.9 kg/m2). Mean weight and percentage fat losses among the 89 completers were −5.4 kg and −3.4%, respectively ( p < .001). A higher number of recent dieting attempts and recent weight loss, more stringent weight outcome evaluations, a higher perceived negative impact of weight on quality of life, lower self-motivation, higher body size dissatisfaction, and lower self-esteem were associated with less weight loss and significantly distinguished responders from nonresponders among all participants. These findings are discussed as to their usefulness (i) to screen individuals before treatment, (ii) to provide a better match interventions to participants, and (iii) to build a weight loss readiness questionnaire.