Protein intake and prevalence of overweight in patients with phenylketonuria: A 10-year longitudinal study

Overweight has been identified as a comorbidity associated with phenylketonuria (PKU). A systematic review with meta-analysis found that although patients with PKU had a similar body mass index (BMI) when compared to non-PKU controls, there was a significantly higher BMI when measured in patients described as having classical PKU.

The aim of this retrospective longitudinal study was to identify the prevalence of overweight in patients with PKU, over 10 years, in a Portuguese Reference Centre, following a phenylalanine-restricted diet.

Inclusion criteria were diagnosis of PKU and completion of an annual nutritional status evaluation every 2 years. Information on anthropometry, dietary intake and blood phenylalanine levels was collected.

The sample consisted of 94 patients (aged 14.0 ± 7.8y, 46 females). Over the study period, there was a non-statistically significant trend towards an increase in the prevalence of overweight (24.5 vs 33.0 %), as defined by age-appropriate BMI. When compared with normal-weight patients, overweight patients had significantly higher blood phenylalanine levels in the first and fifth biennium. Total and natural protein intake were significantly higher in normal-weight patients, at all timepoints, compared to overweight patients. Univariate analysis showed that a higher protein intake, particularly of natural protein, is a protective factor against the development of overweight. This result remained after adjusting total protein intake for age, gender, and metabolic control.

This study found a trend towards an increase in the prevalence of overweight in patients with PKU. Therefore, the nutritional status of patients with PKU should be regularly monitored, supported by preventive and attentive nutritional support.