Childhood Body Composition May Help Determine Future Lung Health

How well we breathe as adults may depend on the amount of fat mass and lean body mass, or muscle, we have as children, according to new research published online in the American Journal of Respiratory and Critical Care Medicine.

Researchers report that boys and girls with more muscle mass in childhood and adolescence have higher lung function. The researchers also found that boys, but not girls, with more fat mass have lower lung function. Previous studies have looked at the association between overall body mass and lung function, but they found contradictory results.

“Some studies related higher body mass with higher lung function while others found higher body mass related to lower lung function,” said Dr. Garcia-Aymerich, senior study author and  head of non-communicable diseases at the Barcelona Institute for Global Health (ISGlobal). “We hypothesized that these contradictory results could be attributed to the fact that overall body mass does not account for the different contribution of fat and muscle mass.”

In the current study, the authors combined body measurements and measurements produced using dual-energy X-ray absorptiometry to distinguish between muscle mass and fat mass. Using commonlung function tests, the researchers also measured lung function in 6,964 children at ages 8 and 15 and calculated the growth in lung function during that time.

Specifically, the study found:

• In boys and girls, higher lean body mass trajectories were associated with higher levels and lung growth rates of forced vital capacity (FVC), the total amount of air a person can exhale and taking the deepest breath possible; forced expiratory volume in one second (FEV₁), the amount of air a person can forcefully exhale in one second; and forced expiratory flow at 25-75% (FEF_25-75), a measure of the speed that air comes out of the lungs.
• In boys and girls, higher fat mass was associated with lower levels of FEV₁/FVC, a measure of airflow limitation often used to help diagnose asthma and chronic obstructive pulmonary disease (COPD).
• In boys, but not girls, higher fat mass was associated with lower levels and lung growth rates of FEV₁ and FEF_25-75.

The researchers adjusted their results for a number of factors that might have biased results including birthweight, maternal smoking during pregnancy and the age of the children at puberty, as well as lung function levels at age eight.

The authors believe their study has important research and public health implications. Body composition, and not just overall body mass, should be assessed when studying the health effects of weight in children, according to the researchers. They added that body composition in childhood and adolescence may play a role in future respiratory health.

“Public health strategies promoting healthy lifestyles may improve lung function and reduce respiratory morbidity in adult life,” Dr. Garcia-Aymerich said. “Such strategies should aim to not only reduce body weight but also reduce fat and increase muscle mass.”