Tyler A. Bosch

Visceral adipose tissue measured by DXA correlates with measurement by CT and is associated with cardiometabolic risk factors in children

Visceral adipose tissue (VAT) generally demonstrates a stronger relationship with cardiometabolic risk factors than total body fat or subcutaneous adipose tissue.

Body Composition and Bone Mineral Density of National Football League Players

Abstract Dengel, DR, Bosch, TA, Burruss, TP, Fielding, KA, Engel, BE, Weir, NL, and Weston, TD. Body composition and bone mineral density of national football league players. J Strength Cond Res 28(1): 1–6, 2014—The purpose of the present study was to examine the body composition of National Football League (NFL) players before the start of the regular season. Four hundred eleven NFL players were measured for height, weight and lean, fat, and bone mass using dual-energy x-ray absorptiometry (DXA). Subjects were categorized by their offensive or defensive position for comparison. On average, positions that mirror each other (i.e., offensive lineman [OL] vs. defensive lineman [DL]) have very similar body composition. Although OL had more fat mass than DL, they were similar in total and upper and lower lean mass. Linebackers (LB) and running backs (RB) were similar for all measures of fat and lean mass. Tight ends were unique in that they were similar to RB and LB on measures of fat mass; however, they had greater lean mass than both RB and LB and upper-body lean mass that was similar to OL. Quarterbacks and punters/kickers were similar in fat and lean masses. All positions had normal levels of bone mineral density. The DXA allowed us to measure differences in lean mass between arms and legs for symmetry assessments. Although most individuals had similar totals of lean mass in each leg and or arms, there were outliers who may be at risk for injury. The data presented demonstrate not only differences in total body composition, but also show regional body composition differences that may provide positional templates.

Abdominal body composition differences in NFL football players.

Abstract Bosch, TA, Burruss, TP, Weir, NL, Fielding, KA, Engel, BE, Weston, TD, and Dengel, DR. Abdominal body composition differences in NFL football players. J Strength Cond Res 28(12): 3313–3319, 2014—The purpose of this study was to examine visceral fat mass as well as other measures abdominal body composition in National Football League (NFL) players before the start of the season. Three hundred and seventy NFL football players were measured before the start of the season using dual-energy x-ray absorptiometry. Regional fat and lean mass was measured for each player. Players were categorized into 3 groups based on positions that mirror each other: linemen; linebackers/tight ends/running backs and wide receivers/defensive backs. Significant differences were observed between the position groups for both lean and fat regional measurements. However, the magnitude of difference was much greater for fat measures than lean measures. Additionally, a threshold was observed (∼114 kg) at which there is a greater increase in fat accumulation than lean mass accumulation. The increase in fat accumulation is distributed to the abdominal region where thresholds were observed for subcutaneous abdominal fat accumulation (12.1% body fat) and visceral abdominal fat accumulation (20.1% body fat), which likely explains the regional fat differences between groups. The results of this study suggest that as players get larger, there is more total fat than total lean mass accumulation and more fat is distributed to the abdominal region. This is of importance as increased fat mass may be detrimental to performance at certain positions. The thresholds observed for increased abdominal fat accumulation should be monitored closely given recent research observed that abdominal obesity predicts lower extremity injury risk and visceral adipose tissues established association with cardiometabolic risk.

Visceral adiposity in persons with chronic spinal cord injury determined by dual energy X-ray absorptiometry.

To determine visceral adipose tissue (VAT) volume (VATvol) by dual energy X‐ray absorptiometry (DXA) in spinal cord injured (SCI) and able‐bodied (AB) participants and to explore the relationships between VATvol and routine anthropometric measures.

Twenty year fitness trends in young adults and incidence of prediabetes and diabetes: the CARDIA study

Aims/hypothesisThe prospective association between cardiorespiratory fitness (CRF) measured in young adulthood and middle age on development of prediabetes, defined as impaired fasting glucose and/or impaired glucose tolerance, or diabetes by middle age remains unknown. We hypothesised that higher fitness levels would be associated with reduced risk for developing incident prediabetes/diabetes by middle age.MethodsParticipants were from the Coronary Artery Risk Development in Young Adults (CARDIA) study who were free from prediabetes/diabetes at baseline (year 0 [Y0]: 1985–1986). CRF was quantified by treadmill duration (converted to metabolic equivalents [METs]) at Y0, Y7 and Y20 and prediabetes/diabetes status was assessed at Y0, Y7, Y10, Y15, Y20 and Y25. We use an extended Cox model with CRF as the primary time-varying exposure. BMI was included as a time-varying covariate. The outcome was development of either prediabetes or diabetes after Y0. Model 1 included age, race, sex, field centre, CRF and BMI. Model 2 additionally included baseline (Y0) smoking, energy intake, alcohol intake, education, systolic BP, BP medication use and lipid profile.ResultsHigher fitness was associated with lower risk for developing incident prediabetes/diabetes (difference of 1 MET: HR 0.99898 [95% CI 0.99861, 0.99940], p < 0.01), which persisted (difference of 1 MET: HR 0.99872 [95% CI 0.99840, 0.99904], p < 0.01] when adjusting for covariates.Conclusions/interpretationExamining participants who had fitness measured from young adulthood to middle age, we found that fitness was associated with lower risk for developing prediabetes/diabetes, even when adjusting for BMI over this time period. These findings emphasise the importance of fitness in reducing the health burden of prediabetes and diabetes.

Identification of sex-specific thresholds for accumulation of visceral adipose tissue in adults

The purpose of this study was to measure the linearity of visceral adipose tissue (VAT) accumulation with measures of total body adiposity to determine whether a threshold exists and to explore the association with cardiometabolic risk factors in adults.

Impaired cardiac autonomic nervous system function is associated with pediatric hypertension independent of adiposity.

Background:We examined whether sympathetic nervous system activity influences hypertension status and systolic blood pressure (SBP) independent of adiposity in youth ranging from normal-weight to severe obesity.Methods:We examined the association of heart rate variability (HRV) with hypertension status and SBP among youth (6–18 y old; n = 188; 103 female). Seated SBP was measured using an automated cuff. Prehypertension (SBP percentile ≥ 90th to <95th) and hypertension (SBP percentile ≥ 95th) were defined by age-, sex-, and height-norms. Autonomic nervous system activity was measured using HRV via SphygmoCor MM3 system and analyzed for time- and frequency-domains. Total body fat was measured via dual-energy X-ray absorptiometry.Results:Logistic regression models demonstrated lower values in each time-domain HRV measure and larger low-frequency (LF):high-frequency (HF) ratio to be significantly associated with higher odds of being prehypertensive/hypertensive (11–47% higher odds) independent of total body fat (P < 0.05). In linear regression analysis, lower time-domain, but not frequency-domain, HRV measures were significantly associated with higher SBP independent of total body fat (P < 0.05).Conclusion:These data suggest that impaired cardiac autonomic nervous system function, at rest, is associated with higher odds of being prehypertensive/hypertensive and higher SBP which may be independent of adiposity in youth.

In adult twins, visceral fat accumulation depends more on exceeding sex-specific adiposity thresholds than on genetics.

OBJECTIVE We recently reported sex-specific percent body fat (%BF) thresholds (males=23%, females=38%) above which, visceral adipose tissue (VAT) significantly increases. Using monozygotic (MZ) and dizygotic (DZ) twins, we examined the influence of genetics on regional fat distribution measured by dual-energy X-ray absorptiometry, above and below these sex-specific thresholds for VAT accumulation. METHODS Fifty-eight twin pairs (44 MZ, 14 DZ) were recruited from the University of Washington Twin Registry. Segmented linear regression was used to assess the threshold between VAT mass and %BF by sex and by zygosity. To assess the effect of genetics on VAT accumulation, Dunnetts T3 compared MZ and DZ pairs whether the twin pairs were both above the adiposity threshold or not. RESULTS %BF thresholds for VAT accumulation were identified (%BF: M=20.6%, F=39.4%). Zygosity-specific thresholds were not significantly different (p>0.05). If at least one twin was below threshold, DZ twins still exhibited greater within-pair differences than MZ pairs in %BF (p=0.023) but not VAT (p=0.121). CONCLUSIONS Using a twin study approach, we observed no difference by zygosity for the threshold as which VAT accumulates. Additionally, for the first time we observed that while total BF is influenced by genetics, VAT accumulation may depend more on whether a persons %BF is above their sex-specific adiposity threshold. These results suggest that there may not be a genetic predisposition for VAT accumulation but rather it is a result of a predisposition for total fat accumulation.

DXA-Determined Regional Adiposity Relates to Insulin Resistance in a Young Adult Population with Overweight and Obesity

Obesity is a well-established risk factor for insulin resistance and type 2 diabetes mellitus, and body fat distribution has important implications for this metabolic risk. In this cross-sectional study, we used dual X-ray absorptiometry body composition data from 123 young adult participants with overweight or obesity, and correlatedwith 2 indices of insulin resistance calculated from oral glucose tolerance tests. Participants were 70% women, with mean (standard error) age 30.1 (0.6) yr, body mass index (BMI) 34.0 (0.6) kg/m2, homeostatic model assessment of insulin resistance (HOMA-IR) of 2.1 (0.2), and Matsuda insulin sensitivity index (Matsuda ISI) of 5.8 (0.4). In women, the strongest correlations were observed with the android-to-gynoid ratio (r = 0.52, p < 0.001 for HOMA-IR; r = -0.46, p < 0.001 for Matsuda ISI), and these correlations remained significant after adjustment for BMI. For men, the strongest correlations were with android fat mass (r = 0.40, p = 0.01 for HOMA-IR; r = -0.37, p = 0.02 for Matsuda ISI). Visceral adipose tissue was correlated with HOMA-IR and Matsuda ISI in women, and only with Matsuda ISI in men. BMI correlated with HOMA-IR and with Matsuda ISI in both women and men. Regional adiposity determined by dual X-ray absorptiometry correlates with indices of insulin resistance in sedentary young adults with overweight and obesity.

The impact of high BMI on acute changes in body composition following 90 min of running

Abstract Objectives: Although physical activity ameliorates the metabolic impact of high body mass index (BMI), runners with BMI ≥25 kg/m2 are relatively understudied. This study had two goals: (1) to identify differences in body composition, as measured by dual X-ray absorptiometry (DXA), between overweight (BMI ≥ 25 kg/m2) runners (OWR) and normal weight (BMI < 25 kg/m2) runners (NWR) and (2) to examine whether a 90-min run alters total or regional fat mass, as measured by DXA, in OWR and NWR. We hypothesized that OWR would have higher total body fat than NWR and OWR with greater changes in visceral fat after a prolonged run. Design: Body composition analysis before and after a supervised run. Methods: We recruited NWR (n = 16, F: n = 7, 28.1 ± 1.4 years, BMI 22.0 ± 0.4 kg/m2, results as mean ± SE) and OWR (n = 11, F: n = 7, 32.0 ± 1.6 years, BMI 30.5 ± 1.4 kg/m2) participants. DXA-based body composition was measured before and after a supervised, 90-min run at 60% heart rate reserve. Results: OWR had higher body fat than NWR in all measured regions. Both groups did not significantly reduce fat mass at any measured fat depots after the running exposure. Conclusions: OWR had higher body fat in all measured regions than NWR. DXA could not demonstrate any acute fat mass changes after a prolonged run.