Body composition assessed by the 4-component model and association with lung function in 6–12-y-old children with cystic fibrosis

Abstract

Background: Malnutrition is an indicator of a poor prognosis in patients with cystic fibrosis (CF). Previous body-composition (BC) studies in children with CF used 2-component models (2CMs) to assess fat mass (FM) and fat-free mass (FFM), but to our knowledge no study has used the gold-standard 4-component model (4CM), which allows for a more accurate evaluation of the nature of both elements. Objective: We measured BC by using the 4CM in 6-12-y-old children with CF to 1) compare findings with those of healthy, matched control children and reference data; 2) relate BC to lung spirometry [forced expired volume in 1 s (FEV 1 )]; and 3) compare findings with those from more commonly used 2CM techniques. Design: One hundred clinically stable children with CF (57% girls) aged 6-12 y were measured by using the 4CM. Children with CF underwent spirometry (FEV 1 ). Results: Girls with CF had significantly less FM than did healthy girls, even after adjustment for height and pubertal status; boys with CF had higher body mass index SD scores than did healthy boys. FM in girls was positively associated with the FEV 1 percentage predicted. The 2CM FM was significantly different from the 4CM FM, with differences dependent on sex and condition, although most techniques identified a relation between FM and FEV 1 in girls. Conclusions: Although shorter than healthy children, boys with CF were heavier and had a BC within the normal range; however, girls with CF had lower FM than did healthy girls, and this was associated with poorer lung function. Given the worse prognosis in girls, this finding merits more attention. The reliability of 2CM techniques varied with sex and health status.Am J Clin Nutr 2010;92:1332-43.

Body composition and lung function in cystic fibrosis and their association with adiposity and normal-weight obesity

“…To our knowledge, the inverse relationship between adiposity and lung function has not previously been described in CF. Additional body composition studies in CF have reported either no relationship 21,22 or a positive relationship 23 between adiposity and lung function, although previous studies have focused on younger aged subjects compared to our cohort. The negative associations of excess adiposity on lung function have been described in the non-CF literature 8,9,24 and may reflect a restrictive mass loading effect on the thorax and upper abdomen created by adipose tissue accumulation, pro-inflammatory effects of adipose tissue, and/or general physical deconditioning 24 .…”

“…However, air displacement plethysmography is based on the two-component model of body composition which partitions body weight into fat mass and fat-free mass and is dependent on the assumption that the density of fat-free mass is constant, regardless of age, sex, race, or disease state 31 . Future studies using the four-component model in adult CF, which partitions body weight into fat, water, mineral, and protein, will be of interest to more accurately quantify body composition in CF 23 .…”

Body-composition reference data for simple and reference techniques and a 4-component model: a new UK reference child

“…Some obese children are too large to be successfully scanned by DXA and are difficult to measure by using skinfold-thickness calipers but can undergo plethysmography (42). When hydration varies beyond the normal range, and when patients are able to undergo a wider range of measurements, the 4C model is ideal, as we have shown for obesity (29), acute lymphoblastic leukemia (30), and cystic fibrosis (43). Thus, our reference data should substantially increase the capacity of clinicians to acquire and interpret data in a wide range of diseases, which could contribute to a range of components of clinical management.…”

Body Composition and Pulmonary Function in Cystic Fibrosis

“…Similarly, DXA-derived LBM, which estimates non-bone LBM, was correlated with degree of lung function impairment in adults and with clinical severity score in both children and adults in studies with small sample sizes (7, 13). In contrast, Williams et al (14) studied body composition in 6- to 12-year-olds with PI-CF using a four-compartment model, a technique limited to the research setting. Their study found that girls with PI-CF had a significantly lower fat mass (FM) compared to age-, height-, and puberty-matched controls, and that FM was positively associated with FEV 1 %-predicted.…”