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

Nutrition. 2016 Apr;32(4):447-52. doi: 10.1016/j.nut.2015.10.012. Epub 2015 Oct 30.


Objectives: This study aimed to evaluate the relationship between lung function and body composition in cystic fibrosis (CF) and examine the presence of normal-weight obesity (NWO), a high body fat percentage with a normal body mass index (BMI), in this population.

Methods: In a pilot, cross-sectional study, 32 subjects with CF and a reference group of 20 adults without CF underwent body composition analysis with air displacement plethysmography. NWO was defined as a BMI <25 kg/m(2) and body fat >30% (for women) or >23% (for men). Lung function in subjects with CF was determined by the percentage of predicted forced expiratory volume in 1 s (FEV1% predicted).

Results: Despite lower BMI and fat-free mass index (P < 0.01), fat mass index and percent body fat did not differ between subjects with CF and the reference group. Among subjects with CF, FEV1% predicted was positively associated with fat-free mass index (β = 6.31 ± 2.93, P = 0.04) and inversely associated with fat mass index (β = -6.44 ± 2.93, P = 0.04), after adjusting for age, sex, and BMI. Ten subjects with CF (31%) had NWO, which corresponded with lower fat-free mass index and FEV1% predicted compared with overweight subjects (P = 0.006 and 0.004, respectively).

Conclusions: Excess adiposity, particularly in the form of NWO, was inversely associated with lung function in CF. Larger prospective studies should be undertaken to confirm these findings and determine the long-term metabolic and clinical consequences of excess adiposity in CF. As the lifespan of individuals with CF increases, nutrition screening protocols, which primarily rely on BMI, may require reassessment.

Keywords: Body composition; Cystic fibrosis; Diet; Lung function; Normal-weight obesity; Obesity.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adiposity
  • Adolescent
  • Adult
  • Body Composition*
  • Body Mass Index
  • Cross-Sectional Studies
  • Cystic Fibrosis / complications
  • Cystic Fibrosis / physiopathology*
  • Female
  • Forced Expiratory Volume
  • Humans
  • Lung / physiopathology*
  • Male
  • Nutrition Assessment
  • Obesity / complications
  • Obesity / physiopathology*
  • Overweight / complications
  • Overweight / physiopathology
  • Pilot Projects
  • Plethysmography
  • Young Adult