The Impact of Phenylketonuria on Body Composition in Adults

Patients with phenylketonuria (PKU) must follow a lifelong phenylalanine (Phe)-restricted diet with additional amino acid supplementations, and this may put them at risk for nutritional disturbances. However, the body composition and nutritional status of adult patients with PKU has only been partially explored. The current study aims to assess the body composition of adult patients with PKU using multifrequency bioimpedance analysis (MF-BIA) and to reveal potential correlations between therapy adherence and body composition. Additionally, we compared body composition of patients with healthy controls.

Fifty adult patients with early-treated PKU (27 female and 23 male) and 40 healthy, age- and gender-matched controls were included in this single-center, cross-sectional study. MF-BIA was performed on all subjects. Additionally, we determined serum nutritional markers for all patients. In the PKU patient group, correlation analyses were performed between body composition parameters and therapy adherence. We compared body composition of patients with PKU and controls using BIA.

The proportion of overweight was 56% among all patients with PKU. Female patients with PKU had significantly higher body fat percentage compared with controls. In parallel with higher fat content, we observed lower muscle mass, protein, and mineral content among female patients with PKU compared to controls. Such findings were not observed in male patients. Female patients with PKU had decreased therapy adherence and had significantly lower prealbumin levels compared with males. There was no significant correlation observed between body composition parameters and therapy adherence over the last 10 years in the PKU patient group.

Although female patients had less optimal therapy adherence over the last 10 years compared with male patients, our results suggest that this does not influence body composition fundamentally. Our results suggest that obesity is an important comorbidity in young adult patients with PKU, especially in females. We advocate that nutritional assessments and weight management should be additional objectives of PKU management to provide optimal care.