The Effect of Triheptanoin on Fatty Acid Oxidation and Exercise Tolerance in Patients With Glycogenoses

The aim of this study is to investigate the effect of 14 days of treatment with the dietary oil-supplement Triheptanoin on fat metabolism and exercise tolerance in patients with Phosphofructokinase deficiency, Debrancher deficiency and Glycogenin-1 deficiency. The investigators wish to investigate whether a Triheptanoin diet can improve exercise capacity by measuring: 1. Heart rate during cycling exercise and maximal exercise capacity 2. Fat and glucose metabolism 3. Concentrations of metabolic substrates in blood during exercise 4. Perception of fatigue and symptoms by questionnaire 5. Degree of exhaustion during cycling exercise by Borg score All measurements are done before and after 14 days with a Triheptanoin-oil diet, and before and after 14 days diet with safflower (Placebo-oil). Triheptanoin-oil supplementation in the diet has been shown to increase metabolism of both fat and carbohydrates in patients with other metabolic myopathies. In these patients, Triheptanoin improved physical performance and has reduced the amount of symptoms experienced by patients.