Low-phenylalanine diets are commonly prescribed to people with phenylketonuria (PKU), an inborn disease which causes accumulation of amino acid phenylalanine (Phe) in the blood. High blood Phe levels can cause mental, behavioural, neurological, and physical problems. Thus, low-phenylalanine diets help patients to manage their condition but it is not clear whether they have an impact on appetite, energy intake and changes in body weight. This is important to explore as prevalence of obesity in this population is rising high. This study aims to find out the effect of PKU-type meals on appetite, appetite biomarkers, and post-meal energy expenditure. The investigators will recruit 26 healthy adults and ask them to participate in two experimental trials. On one occasion the participants will be asked to consume a PKU-supplemented drink followed by a PKU type-lunch and on another occasion the supplement and lunch will be based on normally consumed foods. Series of blood samples will be taken and appetite will be assessed during both experiments. Both experimental trials will finish with consuming an "all-you-can-eat" buffet.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Masking
SINGLE
Enrollment
26
Breakfast, lunch and open buffet dinner
Breakfast, lunch and open buffet dinner
Human Nutrition, School of Medicine, University of Glasgow
Glasgow, United Kingdom
Appetite hormone: peptide YY (PYY)
Plasma concentration at baseline (0 minute) and after ingestion of supplement (at 30, 60 and 90 minutes) and lunch (at 120, 150,180, 210, 240, 270 and 300 minutes)
Time frame: 300 minutes
Appetite hormone: glucagon-like peptide-1 (GLP-1)
Plasma concentration at baseline (0 minute) and after ingestion of supplement (at 30, 60 and 90 minutes) and lunch (at 120, 150,180, 210, 240, 270 and 300 minutes)
Time frame: 300 minutes
Appetite hormone: cholecystokinin (CCK)
Plasma concentration at baseline (0 minute) and after ingestion of supplement (at 30, 60 and 90 minutes) and lunch (at 120, 150,180, 210, 240, 270 and 300 minutes)
Time frame: 300 minutes
Appetite hormone: insulin
Plasma concentration at baseline (0 minute) and after ingestion of supplement (at 30, 60 and 90 minutes) and lunch (at 120, 150,180, 210, 240, 270 and 300 minutes)
Time frame: 300 minutes
Appetite hormone: ghrelin
Plasma concentration at baseline (0 minute) and after ingestion of supplement (at 30, 60 and 90 minutes) and lunch (at 120, 150,180, 210, 240, 270 and 300 minutes)
Time frame: 300 minutes
Subjective appetite score
Visual analogue scale (VAS) collected at baseline and after each blood sample collection
Time frame: 300 minutes
Diet induced thermogenesis
Metabolic rate by means of computerised open-circuit ventilated hood system collected at baseline and after each blood sample collection for the duration of 20 minutes
Time frame: 300 minutes
Taste perception of PKU supplements/foods
Immediately after supplement ingestion and lunch consumption
Time frame: 10 minutes
Consumption time for PKU supplements/foods
Maximum 5 minutes for supplement ingestion and maximum 20 minutes for lunch consumption
Time frame: 20 minutes
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