A 28-year-old woman with a 10-year history of progressive muscle weakness, myalgia, and recurrent rhabdomyolysis is found to have elevated plasma long-chain acylcarnitines, normal ammonia, and normal liver function. Muscle biopsy shows lipid storage myopathy. Genetic testing confirms very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. She is currently on a standard diet with no dietary restrictions. What is the most appropriate next step in management?