Low-Calorie Ketogenic Diet with Continuous Positive Airway Pressure to Alleviate Severe Obstructive Sleep Apnea Syndrome in Patients with Obesity Scheduled for Bariatric/Metabolic Surgery: a Pilot, Prospective, Randomized Multicenter Comparative Study

Obstructive sleep apnea syndrome (OSAS) and obesity are frequently associated with hypertension (HTN), dyslipidemia (DLP), and insulin resistance (IR). In patients with obesity and OSAS scheduled for bariatric surgery (BS), guidelines recommend at least 4 weeks of preoperative continuous positive airway pressure (CPAP). Low-calorie ketogenic diets (LCKDs) promote pre-BS weight loss (WL) and improve HTN, DLP, and IR. However, it is unclear whether pre-BS LCKD with CPAP improves OSAS more than CPAP alone. We assessed the clinical advantage of pre-BS CPAP and LCKD in patients with obesity and OSAS. Seventy patients with obesity and OSAS were randomly assigned to CPAP or CPAP+LCKD groups for 4 weeks. The effect of each intervention on the apnea–hypopnea index (AHI) was the primary endpoint. WL, C-reactive protein (CRP) levels, HTN, DLP, and IR were secondary endpoints. AHI scores improved significantly in both groups (CPAP, p =0.0231; CPAP+LCKD, p =0.0272). However, combining CPAP and LCKD registered no advantage on the AHI score ( p =0.863). Furthermore, body weight, CRP levels, and systolic/diastolic blood pressure were significantly reduced in the CPAP+LCKD group after 4 weeks ( p =0.0052, p =0.0161, p =0.0008, and p =0.0007 vs baseline, respectively), and CPAP+LCKD had a greater impact on CRP levels than CPAP alone ( p =0.0329). The CPAP+LCKD group also registered a significant reduction in serum cholesterol, LDL, and triglyceride levels ( p =0.0183, p =0.0198, and p