Increased Total and Resting Energy Expenditure in Children with Cystic Fibrosis

Abstract 2078 Pulmonary: Cystic Fibrosis Poster Symposium, Tuesday, 5/4

Reduced growth is common in children with cystic fibrosis (CF) and may be caused by increased energy expenditure. The purpose of this investigation was to examine the components of energy expenditure in a group of school age prepubescent children with CF and age matched, healthy children. Respiratory calorimetry was used to measure resting energy expenditure(REE); the doubly labeled water method was used to measure total body water (TBW) and total energy expenditure (TEE) over a 1 week period in all children. The difference between TEE and REE primarily reflects the energy expended in physical activity. Seven patients with CF were studied: age 8.1±1.4 yr, weight 21.6±3.5 kg, length 123.1±5.5 cm (all values mean±SD). All patients had a diagnosis of CF based on results of 2 positive sweat tests. Pulmonary function tests were performed on all patients prior to study to determine the severity of pulmonary disease. Forced expiratory volumes in 1 second (FEV₁) ranged from 44-95% of normal; all patients were receiving pancreatic enzyme supplements at the time of study. Twelve age matched healthy controls (CTL) were also studied: age 8.1±1.5 yr, weight 27.2±7.3 kg, length 131.0±12.0 cm. CF children plotted significantly below controls in both weight and length for age: 13 vs. 60 percentile for weight (CF vs. CTL), and 32 vs. 71 percentile for length (CF vs. CTL).

Results are summarized below. All values are expressed as mean ± SD, *p≤0.05 vs. CTL. Results were compared using ANOVA. No significant correlations were found between FEV₁ and either REE or TEE. (Table)

Table 1 No caption available

Conclusions: Children with CF tend to be smaller and leaner than age-matched healthy children. Children with CF have significantly increased REE and TEE compared to healthy children. This increased TEE is due to both increased REE and increased energy of physical activity. Differences in body composition alone do not appear to completely account for differences in energy expenditure in this population. When normalized to lean body mass, CF children have 8% higher REE, 13% higher TEE, and 23% higher energy of physical activity than healthy children. Children with CF do not compensate for higher REE by reducing physical activity. Higher energy expenditure in these children is a contributing factor to the reduced growth seen in these children.