Basal metabolic rate in myotonic dystrophy: evidence against hypometabolism

We studied the basal metabolic rate in 13 males with myotonic dystrophy and 14 normal male subjects. Basal O2 consumption (VO2) and CO2 production (VCO2) were measured by direct gas analysis with a ventilated hood system. Lean body mass was estimated by total body potassium (40K method) and muscle mass by urine creatinine excretion. The basal metabolic rate of patients with myotonic dystrophy was significantly reduced when related to surface area (-9%), but elevated when related to lean body mass (+17%). Previous reports of hypometabolism in myotonic dystrophy did not take into account the amount of muscle wasting in this disorder, and we conclude that in myotonic dystrophy the basal metabolic rate is actually elevated when corrected for lean body mass.