Free-living energy expenditure reduced after deep brain stimulation surgery for Parkinson's disease.

Summary Background:  The clinical picture in Parkinson’s disease (PD) is characterized by bradykinesia, rigidity, resting tremor and postural instability. In advanced stages of the disease, many patients will experience reduced efficacy of medication with fluctuations in symptoms and dyskinesias. Surgical treatment with deep brain stimulation in the subthalamic nucleus (STN-DBS) is now considered the gold standard in fluctuating PD. Many patients experience a gain of weight following the surgery. The aim of this study was to identify possible mechanisms, which may contribute to body weight gain in patients with PD following bilateral STN-DBS surgery. Methods:  Ten patients with PD were studied before bilateral STN-DBS surgery, and seven patients were studied again 3 and 12 months postoperatively. Clinical examination and resting metabolic rate with and without medical treatment was measured before and after STN-DBS. Furthermore, free-living energy expenditure, body composition, energy intake, peak oxygen consumption, maximal workload and leisure time physical activity were measured before and 3 and 12 months after surgery. Results:  The STN-DBS operated patients had a significant weight gain of 4·7 ± 1·6 kg (mean ± SE) 12 months postoperatively, and the weight gain was in the fat mass. The free-living energy expenditure decreased postoperatively 13 ± 4% even though the reported dietary intake was reduced. A decreased energy expenditure took place in the non-resting energy expenditure. The reported daily leisure time activity, peak oxygen consumption and maximal workload were unchanged. Conclusion:  The STN-DBS operated patients have a significant postoperative weight gain, as a result of a decrease in free-living energy expenditure concomitant with an insufficient decrease in energy intake.