The Obesity Factor: How Cardiorespiratory Fitness is Estimated More Accurately in People with Obesity

Practical Aspects of Cardiopulmonary Exercise Testing in Children

The use of cardiopulmonary exercise testing (CPET) in pediatrics provides critical insights into potential physiological causes of unexplained exercise-related complaints or symptoms, as well as specific pathophysiological patterns based on physiological responses or abnormalities. Furthermore, CPET helps evaluate exercise performance in children with chronic (lung/heart) diseases. For instance, it can ascertain any adverse reaction to exercise and estimate the effects of specific treatment measures. It affords a global assessment of the pathophysiological patterns, responses and abnormalities to exercise that is inadequately reflected by resting lung function and/or cardiac function assessment. Clinical interpretation of the results of a CPET in pediatrics requires specific knowledge regarding pathophysiological responses and interpretative strategies that can be adapted to address concerns specific to the child's medical condition or disability.

Association between cardiorespiratory fitness level and insulin resistance in adolescents with various obesity categories

BACKGROUND

An association between cardiorespiratory fitness (CRF) and insulin resistance in obese adolescents, especially in those with various obesity categories, has not been systematically studied. There is a lack of knowledge about the effects of CRF on insulin resistance in severely obese adolescents, despite their continuous rise.

AIM

To investigate the association between CRF and insulin resistance in obese adolescents, with special emphasis on severely obese adolescents.

METHODS

We performed a prospective, cross-sectional study that included 200 pubertal adolescents, 10 years to 18 years of age, who were referred to a tertiary care center due to obesity. According to body mass index (BMI), adolescents were classified as mildly obese (BMI 100% to 120% of the 95^th percentile for age and sex) or severely obese (BMI ≥ 120% of the 95^th percentile for age and sex or ≥ 35 kg/m², whichever was lower). Participant body composition was assessed by bioelectrical impedance analysis. A homeostatic model assessment of insulin resistance (HOMA-IR) was calculated. Maximal oxygen uptake (VO₂max) was determined from submaximal treadmill exercise test. CRF was expressed as VO₂max scaled by total body weight (TBW) (mL/min/kg TBW) or by fat free mass (FFM) (mL/min/kg FFM), and then categorized as poor, intermediate, or good, according to VO₂max terciles. Data were analyzed by statistical software package SPSS (IBM SPSS Statistics for Windows, Version 24.0). P < 0.05 was considered statistically significant.

RESULTS

A weak negative correlation between CRF and HOMA-IR was found [Spearman’s rank correlation coefficient (r_s) = -0.28, P < 0.01 for CRF_TBW; (r_s) = -0.21, P < 0.01 for CRF_FFM]. One-way analysis of variance (ANOVA) revealed a significant main effect of CRF on HOMA-IR [F₍₂₂₀₀₎ = 6.840, P = 0.001 for CRF_TBW; F₍₂₂₀₀₎ = 3.883, P = 0.022 for CRF_FFM]. Subsequent analyses showed that obese adolescents with poor CRF had higher HOMA-IR than obese adolescents with good CRF (P = 0.001 for CRF_TBW; P = 0.018 for CRF_FFM). Two-way ANOVA with Bonferroni correction confirmed significant effect of interaction of CRF level and obesity category on HOMA-IR [F₍₂₂₀₀₎ = 3.292, P = 0.039 for CRF_TBW]. Severely obese adolescents had higher HOMA-IR than those who were mildly obese, with either good or poor CRF. However, HOMA-IR did not differ between severely obese adolescents with good and mildly obese adolescents with poor CRF.

CONCLUSION

CRF is an important determinant of insulin resistance in obese adolescents, regardless of obesity category. Therefore, CRF assessment should be a part of diagnostic procedure, and its improvement should be a therapeutic goal.

Effect of Weight Self-Stigma and Self-Esteem on Aerobic Exercise Capacity in Adult Women with Different Body Compositions

Background: Overweight individuals face weight-related stigmatization, driving self-exclusion from exercise and physical activity. The extent to which weight self-stigma and self-esteem are associated with aerobic capacity remains unclear. Therefore, this study aimed to characterize the cardiopulmonary fitness, weight self-stigma, and self-esteem of overweight women and examine whether weight self-stigma and self-esteem predict cardiopulmonary aerobic capacity. Methods: A cross-sectional study was conducted with 66 women stratified into two groups: a normal weight (NW) group and an overweight (OW) group. The mean body mass indexes and ages of the NW and OW groups were 20.4 ± 0.36 kg/m² and 29.5 ± 0.8 kg/m², and 24 ± 7 years and 21 ± 3 years, respectively. Submaximal exercise testing using the modified Bruce treadmill protocol was conducted to measure the predicted oxygen uptake (VO_{2 peak}) and energy expenditure. The Weight Self-Stigma Questionnaire and the Rosenberg Self-Esteem Scale were used. Results: Significantly lower mean of predicted VO_{2 peak} and higher mean of energy expenditure were reported in the OW group compared with the NW group (25.8 ± 5.3 mL/kg/min vs. 28.7 ± 4.8 mL/kg/min, p = 0.001 and 9.7 ± 1.9 kcal/min vs. 7.5 ± 1.8 kcal, p = 0.03, respectively). There was a significant difference in weight self-stigma and self-esteem between the groups. Regression model analysis indicated that weight self-stigma and self-esteem explained 45% of the variance in the predicted VO_{2 peak}. Conclusion: Strategies enhancing self-esteem and avoiding stigmatization should be embraced to promote fitness and engagement in physical activity among OW women.

Physical activity is favorably associated with arterial stiffness in patients with obesity and elevated metabolic risk

OBJECTIVES

Physical activity and cardiorespiratory fitness (CRF) are relevant modifiers of cardiovascular risk. Their independent effects on arterial stiffness have not been assessed in people with obesity. This study aimed to assess the independent effects of light (LPA) and moderate-to-vigorous (MVPA) physical activity and CRF on Pulse wave velocity (PWV).

METHODS

Brachial-ankle PWV (baPWV) was measured cross-sectionally in 55 subjects (43.0 ± 13.8 years; 66% women) with moderate cardiovascular risk. Body composition was assessed with bioelectrical impedance-analysis. Daily minutes of LPA and MVPA were measured by accelerometry and CRF (peak oxygen uptake [VO₂ peak]) with spiroergometry. Independent effects of LPA, MVPA, and VO₂ peak on baPWV were analyzed in an age-, sex-, body fat mass-, and blood pressure-adjusted ANOVA.

RESULTS

Every 10 minutes increase of daily MVPA was associated with a 2.8% (0.32m/s [-0.64 to 0.001 m/s], P = .05) reduction of baPWV, whereas LPA and VO₂ peak had only a little or no relevant effects on baPWV.

CONCLUSIONS

Higher MVPA is associated with lower composite arterial stiffness independent of CRF and the number of metabolic risk factors in patients with obesity and further metabolic risk factors. Thus, lifestyle interventions should aim for an increase in MVPA. BaPWV may improve the monitoring of favorable effects of MVPA, even if an improvement of VO₂ peak cannot be obtained.

Obesity, risk of diabetes and role of physical activity, exercise training and cardiorespiratory fitness

The epidemic of obesity contributes to the burden of type 2 diabetes mellitus (T2DM) in the United States and worldwide. Importantly, obesity is not only preventable but can be treated, particularly with lifestyle modifications to forestall T2DM in those with excess adiposity. The mechanisms linking obesity to T2DM are numerous and involve adipose tissue remodeling as a result of unhealthy behaviors, including unhealthy diet, reduced physical activity (PA) and exercise training (ET), and increased sedentary behaviors. Taken together, these factors markedly reduce cardiorespiratory fitness (CRF), one of the strongest predictors for cardiovascular outcomes and all-cause mortality in the general population, but also in those with T2DM. In this review we describe the mechanisms leading to adipose tissue remodeling resulting in obesity, as well as the mechanisms linking excess adiposity to insulin resistance and, in turn, T2DM. We then present the therapeutic strategies that can be implemented in obesity to prevent T2DM, with a brief discussion on weight loss, and greater emphasis on PA and ET. We finally present the evidence to support the beneficial effects of such strategies in patients with established T2DM and discuss the importance of achieving improvements in CRF in this population to potentially improve clinical outcomes.