Among men with obesity, intranasal oxytocin administration led to reduced food intake following an overnight fast vs. men who received an intranasal placebo, according to recent study results.

“We demonstrate that the acute intranasal administration of oxytocin inhibits reward-[driven] but also hunger-driven food intake in obese men and that this effect is not compensated for by changes in energy expenditure,” Matthias Thienel, a doctoral student at the Institute for Medical Psychology and Behavioural Neurobiology at the University of Tubingen, Germany, and colleagues wrote. “In normal-weight men, the oxytocin-induced reduction in calorie consumption was restricted to snacking, indicating that the inhibitory effect of oxytocin on food intake is generally larger in obese than normal-weight subjects.”

Researchers analyzed data from 18 healthy men with obesity and 20 normal-weight men. Each person took part in two experimental sessions 10 days apart following an overnight fast. Participants received either intranasal 24 IU oxytocin (0.6 mL Syntocinon, Defiante Farmacêutica) or placebo at 6 individual puffs (3 per alternating nostril) at 30-second intervals. Participants were presented with a free-choice breakfast buffet 45 minutes later; casual snack intake was assessed 95 minutes later under the pretext of a “snack taste test.” Men underwent olfactory function tests and rated feelings of hunger, mood, subjective wellbeing and perceived experimenter’s trustworthiness on visual analogue scales (1-100). Resting energy expenditure and respiratory quotient were measured via indirect calorimetry. Serum insulin, C-peptide cortisol, growth hormone, plasma glucose, lactate, adrenocorticotropic hormone and non-esterified fatty acids were measured.

Researchers found that, among men with obesity, oxytocin reduced overall food consumption from the breakfast buffet by approximately 10% (P < .04 for treatment) vs. placebo, whereas normal-weight men did not alter their breakfast consumption following oxytocin administration. Both men with obesity and normal-weight men receiving oxytocin reduced their total snack intake by 22% (P < .001 for treatment). In both groups, oxytocin administration did not affect resting energy expenditure, but did exert a sustained suppressive effect on postprandial glucose and hypothalamic pituitary adrenal axis secretion.

“Oxytocin is known from animal experiments to inhibit feeding after intracerebroventricular but also peripheral administration. In humans, most research has focused on the psychosocial effects of oxytocin, while its impact on eating behavior and metabolic control is only beginning to receive attention,” researcher Manfred Hallschmid, PhD,told Endocrine Today. “We found that intranasal oxytocin acutely decreases food intake in normal-weight and, even more so, in obese men. Available weight loss interventions are of modest or temporary efficacy. Therefore, and considering that intranasally administered oxytocin appears to have a very favorable side-effect profile, the peptide might be efficient in the treatment of obesity and related disorders, in particular because it has also been found to exert improving effects on glucose homeostasis. Nevertheless, long-term trials in larger numbers of subjects are needed to sound the potential of oxytocin in the clinical setting.” – by Regina Schaffer