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 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 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.

Inclusion Criteria:

- Otherwise healthy with normal lung function; prepubescent (Tanner equal to or less
than 3); age and gender specific BMI > 95th percentile, but less than 150% of the 95th
percentile based on the CDC standards or age and gender specific BMI between the 16th
and 84th percentile based on the CDC standards; and ability to perform pulmonary and
exercise test accurately.

Exclusion Criteria:

- Children with significant diseases other than obesity or shortness of breath on
exertion will be excluded. Subjects participating in regular conditioning-type
vigorous exercise two times or more per week will be excluded (i.e., sports training).
Children who are non-English speaking will be excluded from the study because the
tests performed are very effort dependent, detailed, and require technical
communication between the staff and the child.