Oxytocin, Weight Loss and Ketosis in Response to a Very-Low-Calorie Ketogenic Diet: An Exploratory Study

Background/Objectives: Obesity is a chronic relapsing disorder associated with many comorbidities. Some evidence suggests that oxytocin (OT) has an anorexigenic effect, but its levels are often increased in obesity. This study investigates the effects of weight loss induced by a very-low-calorie ketogenic diet (VLCKD) on oxytocin levels. Methods: A total of 47 subjects with overweight or obesity, 28 females (60%) and 19 males, with a mean age of 55.5 ± 7.3 years and mean BMI 35.9 ± 4.4 kg/m², underwent VLCKD for 45 days. We assessed anthropometric parameters, metabolic profile, body composition and OT levels at baseline (t0) and at the end of the diet (t1). Results: After weight loss, plasma OT levels significantly dropped. Baseline OT correlated with BMI, fat mass and trunk fat. A linear relationship was observed between Delta OT levels and Delta BMI. Baseline OT was an independent predictor of weight loss and directly correlated with blood ketone levels at the end of the study. An optimal serum OT cut-off that predicts ketosis occurrence was identified. Conclusions: Weight loss obtained with a VLCKD reduces OT levels in patients with excess weight. Baseline OT predicts weight loss and correlates with ketone body levels during a VLCKD.