Feasibility and Tolerability of Nabilone for the Treatment of Obesity: A Randomized Controlled Pilot Trial

Introduction: In epidemiological studies, people who use cannabis have a lower prevalence of obesity. Furthermore, the endocannabinoid system is recognized as a potential target for obesity treatment and partial agonism of the cannabinoid type-1 (CB₁) receptor may reduce body weight. We thus hypothesized that 12 weeks of pharmacotherapy with the partial CB₁ receptor agonist nabilone would reduce body weight, relative to placebo, in adults with obesity. Methods: We conducted a randomized, double-blind, placebo-controlled pilot clinical trial that investigated the feasibility, tolerability, and efficacy of 12 weeks of treatment with nabilone compared with placebo in adults with obesity. Otherwise healthy adults aged 25-45 years with obesity were randomized in a 1:1:1 ratio to one of three parallel treatment arms: high-dose nabilone (6 mg/day), low-dose nabilone (2 mg/day), or placebo. Safety and feasibility outcomes included adverse events (AEs), number of dropouts, and medication adherence per treatment arm. Efficacy outcomes included body weight, body mass index (BMI), and waist circumference. Secondary outcomes included gut microbiome changes, blood biomarkers (e.g., glucose and insulin levels), and mood. Results: Overall, 18 participants were randomized and 15 participants received at least one dose of drug (4 high-dose arm, 5 low-dose arm, 6 placebo). The trial was terminated early due to poor tolerability of the medication (e.g., all four participants allocated to high-dose nabilone withdrew due to AEs). Only eight participants completed per protocol (four in the low-dose arm and four in the placebo arm). Using data from completers only (n = 8), we saw a significant treatment effect on body weight (p < 0.001) and BMI (p < 0.001) that appeared to be driven by greater decreases in the low-dose arm (n = 4) relative to placebo (n = 4). Based on the Bray-Curtis dissimilarity, the low-dose arm showed a greater change in the overall fecal microbiome composition compared with the placebo arm (p < 0.05). Discussion: This pilot trial found poor tolerability of nabilone pharmacotherapy (especially at 6 mg/day) for adults with obesity who had not used any cannabinoid drugs for 6 months prior to enrolment. Preliminary results suggest a possible impact of nabilone on the gut microbiome.