Respiratory Effects of Obesity in Children

In obese children, excess fat exerts an unfavorable burden on the respiratory system, particularly during exercise, potentially reducing exercise tolerance and leading to DOE (dyspnea on exertion), which could explain reports of low physical activity and fitness levels in obese children. The investigators propose that most of the respiratory effects in obese children are the result of low lung volume breathing, i.e., a reduction in functional residual capacity (FRC) at rest, and end-expiratory lung volume (EELV) during exercise. The overall objective of this application is to investigate the respiratory effects of obesity in prepubescent children, including obese children with respiratory symptoms misdiagnosed as asthma, before and after 1) a program of weight loss and regular exercise and 2) continued weight gain as compared with normal weight children before and after 1 yr. The investigative approach will be to examine respiratory function, exercise tolerance, and dyspnea on exertion (DOE) in prepubescent obese boys and girls, including those misdiagnosed with asthma (i.e., asthma not confirmed by lung function tests), before and after 1) weight loss (or an equivalent reduction in BMI percentile) and regular exercise and 2) continued weight gain (or an increase in BMI percentile) as compared with prepubescent normal weight boys and girls before and after a control period of 1 yr. Specific Aims: The following hypotheses will be tested in obese children as compared with normal weight children: Aim 1) Obesity will decrease respiratory function but to a greater extent in obese children misdiagnosed with asthma as evidenced by altered pulmonary function and breathing mechanics at rest; Aim 2) Obesity will decrease exercise tolerance (as evidenced by peak maximum oxygen uptake (VO2) in ml/min/kg, i.e., physical fitness), but not cardiorespiratory fitness (as evidenced by peak VO2 in % of predicted based on ideal body wt), except in obese children misdiagnosed with asthma where both may be reduced during graded cycle ergometry; Aim 3) Obesity will increase DOE but to a greater extent in obese children misdiagnosed with asthma as evidenced by increased ratings of perceived breathlessness during constant load exercise cycling; and Aim 4) Weight loss and regular exercise will improve respiratory function, exercise tolerance, and DOE in obese children, including those misdiagnosed with asthma, while continued weight gain will worsen respiratory function, exercise tolerance, and DOE in obese children, including those misdiagnosed with asthma, as compared with normal weight children before and after 1 yr. The long-term objective is to investigate the effects of obesity on respiratory function, exercise tolerance, and DOE, examine obesity-related respiratory symptoms misdiagnosed as asthma in obese children, and provide novel results that could alter interventional approaches for preventing obesity and treating obesity in obese children. Thus, these results will have broad and immediate clinical impact on the care of obese children, especially those with respiratory symptoms misdiagnosed as asthma.