The association between cardiorespiratory fitness and cardiovascular risk may be modulated by known cardiovascular risk factors

Structural, Functional, and Electrical Remodeling of the Atria With Reduced Cardiorespiratory Fitness: Implications for AF

BACKGROUND

Reduced cardiorespiratory fitness (CRF) is an independent risk factor for the progression of atrial fibrillation (AF). We hypothesized that reduced CRF is associated with structural, functional, and electrical remodeling of the left atrium.

OBJECTIVES

This study sought to correlate objectively assessed CRF with functional and electrical left atrial (LA) parameters using invasive and noninvasive assessments.

METHODS

Consecutive patients with symptomatic AF undergoing catheter ablation were recruited. CRF was objectively quantified pre-ablation by using cardiopulmonary exercise testing. Using peak oxygen consumption, participants were classified as preserved CRF (>20 mL/kg/min) or reduced CRF (<20 mL/kg/min). LA stiffness was assessed invasively with hemodynamic monitoring and imaging during high-volume LA saline infusion. LA stiffness was calculated as ΔLA diameter/ΔLA pressure over the course of the infusion. LA function was assessed with echocardiographic measures of LA emptying fraction and LA strain. Electrical remodeling was assessed by using high-density electroanatomical maps for LA voltage and conduction.

RESULTS

In total, 100 participants were recruited; 43 had reduced CRF and 57 had preserved CRF. Patients with reduced CRF displayed elevated LA stiffness (P = 0.004), reduced LA emptying fraction (P = 0.006), and reduced LA reservoir strain (P < 0.001). Reduced CRF was also associated with reduced LA voltage (P = 0.039) with greater heterogeneity (P = 0.027) and conduction slowing (P = 0.04) with greater conduction heterogeneity (P = 0.02). On multivariable analysis, peak oxygen consumption was independently associated with LA stiffness (P = 0.003) and LA conduction velocities (P = 0.04).

CONCLUSIONS

Reduced CRF in patients with AF is independently associated with worse LA disease involving functional and electrical changes. Improving CRF may be a target for restoring LA function in AF.

Low cardiorespiratory fitness is associated with elevated intraocular pressure among apparently healthy adults

PURPOSE

To evaluate the association of cardiorespiratory fitness with elevated intraocular pressure (IOP) in healthy adults.

METHODS

In this cross-sectional study, we evaluated 17,990 asymptomatic self-referred adults free of diabetes or cardiovascular disease who were screened in a preventive healthcare setting. All subjects underwent measurement of IOP and completed a maximal exercise stress test according to the Bruce protocol. Fitness was categorized into age and sex-specific quintiles according to the treadmill time and dichotomized to low (lowest quintile) and non-low fitness groups. Elevated IOP was defined as ≥ 21 mmHg.

RESULTS

Median age was 45 (IQR 39-52) years and 12,073 (67%) were men. There were 3,351 (19%) subjects in the low fitness group. Median IOP was 14 mmHg (IQR 12-16) with elevated IOP documented in 188 (1%) subjects. Univariate binary logistic regression model demonstrated that compared with non-low fitness group, subjects in the low fitness group were 2.2 times more likely to have elevated IOP (95% CI 1.598-2.95, p<0.001). Multivariate binary logistic regression with adjustment to known cardiovascular risk factors (age, sex, hypertension, smoking, overweight, regular physical activity, low HDL cholesterol, high triglycerides, and fasting glucose levels) successfully demonstrated that lower fitness was independently and significantly associated with a 90% increased likelihood of elevated IOP (95% CI 1.37-2.61, p<0.001). Subgroup analysis revealed that the association was more pronounced among women compared with men (OR 3.8 vs. 1.6, p for interaction = 0.069).

CONCLUSIONS

Low cardiorespiratory fitness is independently associated with increased IOP among apparently healthy adults.

Cardiorespiratory Fitness and Risk of Cardiovascular Events and Mortality in Middle Age Patients without Known Cardiovascular Disease

BACKGROUND

Low cardiorespiratory fitness is an established risk predictor for chronic non-communicable diseases. We aimed to investigate the prognostic significance of fitness level on the risk of major adverse cardiac events (MACE, the composite of myocardial infarction, stroke, or all-cause death), in a contemporary cohort of middle-aged subjects without cardiovascular disease.

METHODS

Retrospective analysis of patients aged 40-60 years without a history of cardiovascular disease. Degree of fitness was determined according to a graded, maximal treadmill exercise stress testing (EST) time achieved, classified into age- and sex-specific quintiles (Q), and categorized as low (Q1), moderate (Q2-Q4) or high (Q5) fitness groups. A multivariable Cox proportional hazard regression model was used to assess the association of fitness level with the risk of MACE.

RESULTS

A total of 6836 patients were included, of which 44.5% were women, and the mean age was 52 years. Overall, 289 MACE events occurred during a median follow-up of 7 years. Level of fitness was inversely associated with the presence of cardiovascular risk factors. The multivariable adjusted hazard ratio (95% confidence interval) for MACE was 1.65 (1.12-2.44) and 2.17 (1.40-3.38) in those at moderate and low fitness levels, compared to the high-fitness group (reference), respectively. For each decrease of one metabolic equivalent (MET) unit achieved at peak exercise, the relative risk for MACE increased by 18%. The association between low fitness and MACE was not modified by other risk factors (P-for-interaction non-significant).

CONCLUSIONS

Low fitness level, as captured by a maximal treadmill EST, is an independent risk predictor for MACE among middle-age individuals without known cardiovascular disease. The association of low fitness with high burden of cardiometabolic risk factors highlight the importance of lifestyle intervention in this patient population.

Fit-Fat Index is better associated with heart rate variability compared to fitness and fatness alone as indicators of cardiometabolic human health

OBJECTIVES

Cardiorespiratory fitness and fatness indicators have been related to heart rate variability (HRV) parameters. The Fit-Fat Index (FFI) is a single index combining cardiorespiratory fitness and fatness indicators. To the best of our knowledge, no studies have previously analyzed whether FFI are related to cardiac autonomic nervous system activity assessed through HRV parameters. This study aimed (i) to examine the association of cardiorespiratory fitness, fatness indicators, and FFI with HRV parameters; and (ii) to report what of the different fatness indicators included in FFI is better associated with HRV parameters in sedentary adults.

METHODS

One hundred and fifty healthy adults (74 women; 76 men), aged between 18 and 65 years old, participated in this cross-sectional study. We measured cardiorespiratory fitness (maximal oxygen consumption) and fatness indicators (waist-to-height ratio [WHR], fat mass percentage [FM%] and visceral adipose tissue [VAT]). Three FFIs were calculated as the quotient between cardiorespiratory fitness and one out of three possible fatness indicators: Fit-Fat Index calculated waist-to-height ratio (FFIWHR ), Fit-Fat Index calculated with FM% (FFIFM% ), and Fit-Fat Index calculated with VAT (FFIVAT ). HRV parameters were measured in resting conditions using a Polar RS800CX.

RESULTS

FFIWTHR , FFIFM% and FFIVAT were related to different HRV parameters (β ranges between -0.507 and 0.529; R2 ranges between 0.096 and 0.275; all p < .001) and the association was stronger with HRV parameters than the isolated fitness or fatness indicators (β ranges between -0.483 and 0.518; R2 ranges between 0.071 and 0.263; all p < .001). FFIVAT was the index more consistently associated with HRV parameters (β ranges between -0.507 and 0.529; R2 ranges between 0.235 and 0.275; all p < .001).

CONCLUSION

Our study suggests that compound FFIs are better predictors of HRV parameters than either cardiorespiratory fitness or fatness indicators alone. The FFIVAT was the best index in terms of its association to HRV.

High fitness might be associated with the development of new-onset atrial fibrillation in obese non-athletic adults

BACKGROUND

Data on the association between AF and fitness are conflicting.

OBJECTIVES

The aim of this analysis was to investigate the association between fitness, obesity and incidence of atrial fibrillation (AF) among apparently healthy non-athlete adults.

METHODS

We investigated 20 410 self-referred subjects who were annually screened in a tertiary medical centre. All subjects were free of AF and completed maximal exercise stress test according to the Bruce protocol at baseline. Fitness was categorised into age- and sex-specific quintiles (Q) according to the treadmill time. Subjects were categorised to low (Q1-Q2) and high fitness (Q3-5) groups. The primary end point was new-onset AF during follow-up.

RESULTS

Mean age was 48 ± 10 years and 72% were men. A total of 463 (2.3%) events occurred during an average follow-up of 8 ± 5 years corresponding to an AF event rate of 0.3% per person year. Univariate and multivariate models showed that AF risk was similar in both fitness groups. However, AF event rate was 0.55% per person year among high fitness obese subjects, compared with 0.31% for low fitness obese subjects (P < .01). Subgroup interaction analysis showed that AF risk is obesity-dependent, such that in the obese group (≥30 kg/m² ) high fitness was independently associated with a significant 79% increased AF risk (95% CI 1.15-2.78; P = .01), whereas among non-obese subjects the rate of events was similar between both fitness groups (P for interaction = (.02)).

CONCLUSIONS

Our findings suggest that high fitness might be associated with increased AF risk among obese subjects.

Cardiorespiratory fitness and survival following cancer diagnosis

Aims

Data on the association of cardiorespiratory fitness with survival of cancer patients are limited. This study aimed to evaluate the association between midlife cardiorespiratory fitness and survival after a subsequent cancer diagnosis.

Methods

We evaluated 19,134 asymptomatic self-referred adults who were screened in preventive healthcare settings. All subjects were free of cardiovascular disease and cancer at baseline and completed a maximal exercise stress test. Fitness was categorised into age-specific and sex-specific quintiles according to the treadmill time and dichotomised to low (quintiles 1–2) and high fitness groups.

Results

The mean age was 50 ± 8 years and 72% were men. During a median follow-up of 13 years (interquartile range 7–16) 517 (3%) died. Overall, 1455 (7.6%) subjects developed cancer with a median time to cancer diagnosis of 6.4 years (interquartile range 3–10). Death from the time of cancer diagnosis was significantly lower among the high fitness group (Plog rank = 0.03). Time-dependent analysis showed that subjects who developed cancer during follow-up were more likely to die (P &lt; 0.001). The association of cancer with survival was fitness dependent such that in the lower fitness group cancer was associated with a higher risk of death, whereas among the high fitness group the risk of death was lower (hazard ratio 20 vs. 15; Pfor interaction = 0.047). The effect modification persisted after applying a 4-year blanking period between fitness assessment and cancer diagnosis (Pfor interaction = 0.003).

Conclusion

Higher midlife cardiorespiratory fitness is associated with better survival among cancer patients. Our findings support fitness assessment in preventive healthcare settings.

Cardiorespiratory Fitness and Incident Stroke Types: The FIT (Henry Ford ExercIse Testing) Project

OBJECTIVE

To study the association between cardiorespiratory fitness (CRF) and incident stroke types.

PATIENTS AND METHODS

We studied a retrospective cohort of patients referred for treadmill stress testing in the Henry Ford Health System (Henry Ford ExercIse Testing Project) without history of stroke. CRF was expressed by metabolic equivalents of task (METs). Using appropriate International Classification of Diseases, Ninth Revision codes, incident stroke was ascertained through linkage with administrative claims files and classified as ischemic, hemorrhagic, and subarachnoid hemorrhage (SAH). Multivariable-adjusted Cox proportional hazards models examined the association between CRF and incident stroke.

RESULTS

Among 67,550 patients, mean ± SD age was 54±13 years, 46% (n=31,089) were women, and 64% (n=43,274) were white. After a median follow-up of 5.4 (interquartile range 2.7-8.5) years, a total of 7512 incident strokes occurred (6320 ischemic, 2481 hemorrhagic, and 275 SAH). Overall, there was a graded lower incidence of stroke with higher MET categories. Patients with METs of 12 or more had lower risk of overall stroke [0.42 (95% CI, 0.36-0.49)], ischemic stroke [0.69 (95% CI, 0.58-0.82)], and hemorrhagic stroke [0.71 (95% CI, 0.52-0.95)].

CONCLUSION

In a large ethnically diverse cohort of patients referred for treadmill stress testing, CRF is inversely associated with risk for ischemic and hemorrhagic stroke.

Associations of leisure screen time with cardiometabolic biomarkers in college-aged adults

We examined whether screen time was associated with cardiometabolic disease (CMD) risk factors in young adults. Ninety-five adults (19.9 ± 11.4 years) self-reported medical and health behavior history, screen time (television viewing, video games and computer games), and dietary intake. Waist circumference, blood pressure, fasting glucose and lipid levels, cardiorespiratory fitness (VO₂peak), and body composition were measured. Total sedentary behavior and moderate-to-vigorous physical activity (MVPA) were measured by accelerometer. On average, leisure screen time (2.0 ± 1.6 h day^-1) accounted for 24% of total sedentary time (8.4 ± 1.5 h day^-1). After adjustment for demographics, smoking, sleep duration, total energy intake, total sedentary time and MVPA, a 1-standard deviation increase in leisure screen time was associated with a 26% higher BMI, 29% higher waist circumference, 25% higher fat mass, 23% higher triglyceride, and 24% lower VO₂peak (p < 0.05). Our findings suggest that screen time may contribute to the risk of obesity and CMD in young adults.

Cardiorespiratory Fitness Is an Independent Predictor of Cardiovascular Morbidity and Mortality and Improves Accuracy of Prediction Models

BACKGROUND

Although cardiorespiratory fitness (CRF) is a strong independent predictor of adverse cardiovascular outcomes, it is not considered as a risk enhancer by current guidelines.

METHODS

We evaluated asymptomatic self-referred adults aged 40 to 79 years of age, free of cardiovascular disease at baseline, who were screened annually and completed baseline exercise stress test. Baseline CRF was dichotomized into 2 groups: low (metabolic equivalents < 8) and high. The primary endpoint was the composite of death, nonfatal acute coronary syndrome, and stroke after excluding subjects diagnosed with metastatic cancer during follow-up.

RESULTS

Study population included 15,445 subjects with median age of 49 years (interquartile range: 44-55). During median follow-up of 8 years 1362 (9%) subjects developed the study endpoint. Kaplan-Meier survival analysis showed that both fitness and atherosclerotic cardiovascular disease (ASCVD) were associated with developing of the study endpoint (P < 0.001 for both). Cox regression model with adjustment for ASCVD risk consistently showed that lower fitness was associated with a significant 23% higher risk to develop the study endpoint (P = 0.001). Continuous net reclassification improvement analysis showed an overall improvement of 11.4% (95% confidence interval, 8%-14.6%; P value < 0.001) in the accuracy of classification when fitness was added to the ASCVD model.

CONCLUSIONS

Low CRF is a strong independent predictor of the cardiovascular morbidity and mortality in asymptomatic adults. Addition of fitness to the pooled cohort ASCVD risk significantly improves the accuracy of the model.

Associations of Resistance Exercise with Cardiovascular Disease Morbidity and Mortality

PURPOSE

Resistance exercise (RE) can improve many cardiovascular disease (CVD) risk factors, but specific data on the effects on CVD events and mortality are lacking. We investigated the associations of RE with CVD and all-cause mortality and further examined the mediation effect of body mass index (BMI) between RE and CVD outcomes.

METHODS

We included 12,591 participants (mean age, 47 yr) who received at least two clinical examinations 1987-2006. RE was assessed by a self-reported medical history questionnaire.

RESULTS

During a mean follow-up of 5.4 and 10.5 yr, 205 total CVD events (morbidity and mortality combined) and 276 all-cause deaths occurred, respectively. Compared with no RE, weekly RE frequencies of one, two, three times or total amount of 1-59 min were associated with approximately 40%-70% decreased risk of total CVD events, independent of aerobic exercise (AE) (all P values <0.05). However, there was no significant risk reduction for higher weekly RE of more than four times or ≥60 min. Similar results were observed for CVD morbidity and all-cause mortality. In the stratified analyses by AE, weekly RE of one time or 1-59 min was associated with lower risks of total CVD events and CVD morbidity regardless of meeting the AE guidelines. Our mediation analysis showed that RE was associated with the risk of total CVD events in two ways: RE had a direct U-shaped association with CVD risk (P value for quadratic trend <0.001) and RE indirectly lowered CVD risk by decreasing BMI.

CONCLUSION

Even one time or less than 1 h·wk of RE, independent of AE, is associated with reduced risks of CVD and all-cause mortality. BMI mediates the association of RE with total CVD events.

The effects of a pilates-aerobic program on maximum exercise capacity of adult women

ABSTRACT Introduction: Physical exercise such as the Pilates method offers clinical benefits on the aging process. Likewise, physiologic parameters may be improved through aerobic exercise. Methods: In order to compare the differences of a Pilates-Aerobic intervention program on physiologic parameters such as the maximum heart rate (HRmax), relative maximal oxygen consumption (relative VO2max) and absolute (absolute VOmax), maximum heart rate during maximal oxygen consumption (VO2max-HRmax), maximum minute volume (VE) and forced vital capacity (FVC), a total of 64 adult women (active group = 48.1 ± 6.7 years; control group = 47.2 ± 7.4 years) participated in the study. The physiological parameters, the maximal speed and total duration of test were measured by maximum exercise capacity testing through Bruce protocol. The HRmax was calculated by a cardio-ergometric software. Pulmonary function tests, maximal speed and total time during the physical test were performed in a treadmill (Medisoft, model 870c). Likewise, the spirometry analyzed the impact on oxygen uptake parameters, including FVC and VE. Results: The VO2max (relative and absolute), VE (all, P<0.001), VO2max-HRmax (P<0.05) and maximal speed of treadmill test (P<0.001) showed significant difference in the active group after a physical exercise interventional program. Conclusion: The present study indicates that the Pilates exercises through a continuous training program might significantly improve the cardiovascular system. Hence, mixing strength and aerobic exercises into a training program is considered the optimal mechanism for healthy aging.

Gender disparities in the functional significance of anemia among apparently healthy adults

BACKGROUND

Data on the functional impact of anemia on cardiorespiratory fitness (CRF) and survival in healthy individuals are limited. Our aim was to evaluate the association between anemia thresholds, low CRF, and survival in otherwise healthy adults.

METHODS

Study population included 16 334 apparently healthy subjects attending annual periodic health screening examinations (71 200 annual visits), including exercise stress testing (EST). Anemia was defined by the World Health Organization (WHO) or Beutler and Waalens' (BW) criteria. Low CRF was defined as the lowest fitness quintile according to the Bruce protocol.

RESULTS

The mean age was 46±10 years, and 70% were men. Mean Hb levels were 13±1 and 15±1 among women and men, respectively, with higher proportion of anemia among women. The majority of anemic subjects had mild anemia. When analyzing repeated annual visits, anemia was associated with a significant 39% and 64% increased risk of low CRF according the WHO and BW criteria only in women (n=18 672). Baseline anemia at first visit was associated with 2.6- and 1.9-fold increased risk of all-cause mortality using the WHO and BW criteria, exclusively in men (n=11 511).

CONCLUSIONS

Overall, the functional and prognostic impact of anemia is gender dependent, based on the WHO and BW arbitrary criteria, suggesting differing mechanism and responses.

Poor Heart Rate Recovery Is Associated With the Development of New-Onset Atrial Fibrillation in Middle-Aged Adults

OBJECTIVE

To investigate the association between heart rate recovery (HRR) and new-onset atrial fibrillation (AF) in middle-aged adults.

PATIENTS AND METHODS

Heart rate recovery was calculated using the exercise stress test in 15,729 apparently healthy self-referred men and women who attended periodic health screening examinations between January 2000, and December 2015. All participants completed the maximal exercise stress test according to the Bruce protocol and were followed clinically on a yearly basis for a median of 6.4±4 years. The primary end point was new-onset AF. Participants were grouped according to HRR at 5 minutes, dichotomized at the median value (<73 beats/min).

RESULTS

Participants with low HRR were older, were more commonly men, had a higher rate of comorbidities, and were less fit. Kaplan-Meier survival analysis revealed that the cumulative probability of AF at 6 years was higher in participants with low HRR (2.1%) than in those with high HRR (0.6%) (log-rank, P<.001). Older age, male sex, obesity resting heart rate, and ischemic heart disease were all associated with increased AF risk in a univariate Cox regression model (P<.05 for all). Multivariate Cox regression analysis revealed that low HRR was independently associated with increased AF risk (hazard ratio, 1.92; 95% CI, 1.3-2.8; P<.001) after adjustment for multiple confounders.

CONCLUSION

Lower HRR is independently associated with the development of new-onset AF during long-term follow-up in middle-aged adults.

Cardiorespiratory Fitness and Highly Sensitive Cardiac Troponin Levels in a Preventive Medicine Cohort

BACKGROUND

Cardiorespiratory fitness (CRF) and highly sensitive cardiac troponin T (hs-cTnT) are associated with risk of all-cause and cardiovascular mortality as well as incident heart failure. A link of low CRF to subclinical cardiac injury may explain this association. We hypothesized that CRF would be inversely associated with hs-cTnT measured in healthy adults over age 50.

METHODS AND RESULTS

We evaluated 2498 participants (24.7% female, mean age 58.7 years) from the Cooper Center Longitudinal Study between August 2008 and January 2012. Plasma specimens obtained shortly before CRF estimates by Balke treadmill testing were used for hs-cTnT assays. CRF was grouped into low CRF (category 1), moderate CRF (categories 2-3), and high CRF (categories 4-5). Multivariable logistic regression was used to estimate the association of CRF with hs-cTnT. The prevalence of measurable hs-cTnT (≥3 ng/L) was 78.5%. In multivariable analyses, low-fit individuals were significantly more likely than high-fit individuals to have elevated hs-cTnT (≥14 ng/L) (odds ratio 2.47, 95% CI 1.10-5.36).

CONCLUSIONS

In healthy older adults, CRF is inversely associated with hs-cTnT level adjusted for other risk factors. Prospective studies are needed to evaluate whether improving CRF is effective in preventing subclinical cardiac injury.

Metabolic risk in schoolchildren is associated with low levels of cardiorespiratory fitness, obesity, and parents' nutritional profile

OBJECTIVE

Verify the association between metabolic risk profile in students with different levels of cardiorespiratory fitness and body mass index, as well as the nutritional status of their parents.

METHODS

A cross-sectional study comprising 1.254 schoolchildren aged between seven and 17 years. The metabolic risk profile was calculated by summing the standardized values of high density lipoproteins and low density lipoproteins, triglycerides, glucose and systolic blood pressure. The parents' nutritional status was evaluated by self-reported weight and height data, for body mass index calculating. The body mass index of schoolchildren was classified as underweight/normal weight and overweight/obesity. The cardiorespiratory fitness was assessed by 9-minute running/walk test, being categorized as fit (good levels) and unfit (low levels). Data were analyzed using prevalence ratio values (PR).

RESULTS

The data indicates a higher occurrence of developing metabolic risk in schoolchildren whose mother is obese (PR: 1.50; 95% CI: 1.01, 2.23), and even higher for those whose father and mother are obese (PR: 2, 79, 95% CI: 1.41; 5.51). Students who have low levels of cardiorespiratory fitness and overweight/obesity have higher occurrence of presenting metabolic risk profile (PR: 5.25; 95% CI: 3.31; 8.16).

CONCLUSION

the occurrence of developing metabolic risk in schoolchildren increase when they have low levels of cardiorespiratory fitness and overweight/obesity, and the presence of parental obesity.

Low Cardiorespiratory Fitness Is Associated with Markers of Insulin Resistance in Young, Normal Weight, Hispanic Women

BACKGROUND

Low cardiorespiratory fitness (CRF) and its decline over time are predictors of the development of diabetes in black and Caucasian women, independent of obesity. It is unclear, however, if the adverse effect of low CRF on the risk of diabetes in Hispanic women is mediated by obesity. Our purpose was to determine the associations of CRF with markers of insulin resistance in 68 normal weight Hispanic women.

METHODS

Obesity indicators included body mass index (BMI), body composition by DXA, and waist circumference. CRF was measured by indirect calorimetry. A glucose tolerance test was used to measure markers of insulin resistance: homeostasis model assessment, fasting insulin, 2-hr insulin, area under the curve insulin, qualitative insulin sensitivity check, and insulin sensitivity index. Pearson correlation and multiple regression analyses were used to identify associations between CRF and markers of insulin resistance. Multivariate ANOVA was used to compare markers of insulin resistance over quartiles of CRF.

RESULTS

Low CRF was significantly associated with all markers of insulin resistance (P < 0.01). These associations were independent of age, BMI, waist circumference, family history of T2DM, and triglycerides (CRF standardized beta range: -0.27 to -0.46, P < 0.05). However, these associations were attenuated when body composition, specifically fat-free mass, was entered into the model (CRF standardized beta range: -0.03 to 0.21, P > 0.05). All markers of insulin resistance improved linearly across CRF quartiles (P < 0.05).

CONCLUSIONS

Our findings suggest that low CRF may be an important predictor of diabetes risk in Hispanic women and that fat-free mass rather than overall body adiposity mediates these relationships.