Metabolic diseases and mitochondrial disorders are caused by genetic mutation which lead to disruptions in energy producing pathways in our body. Enough energy or calories must be given in the diet to ensure normal growth and development. Currently, energy needs for patients with metabolic and mitochondrial diseases are not measured, but is estimated using a mathematical equation based on healthy children. This may lead to under feeding or overfeeding of calories, and has negative nutritional implications.

The clinical standard for measuring energy needs is the use of indirect calorimeter.The indirect calorimeter takes individualized measurements for each patient and therefore will enable dietitians and clinicians to provide sufficient calories in the diet to better manage the disease and promote normal growth and development.

We believe daily energy requirements will vary within metabolic diseases (Phenylketonuria) and mitochondrial disorders (mitochondrial fatty acid oxidation defect, POLG1 mutation etc.).

The objective of this preliminary study is to measure resting energy expenditure in children living with metabolic and mitochondrial conditions and data obtained will be used to generate future hypothesis and will form a basis for future studies.

Inclusion Criteria:

• Children(1-18y) who are diagnosed with either Phenylketonuria (PKU) or a mitochondrial disorder

Exclusion Criteria:

• Children, less than 1y old, who are diagnosed with PKU or a mitochondrial disorder, as it is difficult to perform indirect calorimeter on them.
• Children(1-18y) who are not diagnosed with PKU or a mitochondrial disorder
• Children(1-18y) who are diagnosed with either PKU or a mitochondrial disorder, but are currently experiencing illness such as fever, cold, vomiting or diarrhea

Children (1-18y) diagnosed with either phenylketonuria or a mitochondrial disorder