Abstract: Olfaction contributes to feeding behaviour and is modulated by changes in dopamine levels. Methylphenidate (MPH) increases brain dopamine levels and has been shown to reduce appetite and promote weight loss in patients with attention deficit hyperactivity disorder. The objectives of this study were to test the effect of MPH on olfaction, appetite, energy intake, and body weight (BW) on individuals with obesity. In a randomized, double-blind study, 12 participants (age 28.96 6.7 years) with a body mass index (BMI) of 36.16 4.5 kg/m2 were assigned to MPH (0.5 mg/kg) (n = 5) or placebo (n = 7) twice daily for 2 months. Appetite (visual analog scale), odour threshold (Sniffin’ SticksVR), energy intake (food menu), and BW (DEXA scan) were measured at day 1 and day 60. MPH intake significantly increased odour threshold scores (6.36 1.4 vs. 9.46 2.1 and 7.96 2.3 vs. 7.86 1.9, respectively; p = 0.029) versus placebo. There was a significantly greater suppression of appetite sensations (desire to eat (p = 0.001), hunger (p = 0.008), prospective food consumption (p = 0.003)) and an increase in fullness (p = 0.028) over time in the MPH versus placebo. MPH suppressed appetite and improved olfactory sensitivity in individuals with obesity. These data provide novel findings on the favourable effects of MPH on appetite and weight regulation in individuals living with obesity.
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