Eligible participants will be followed for up to 14 months and will be expected to complete 9 in-person visits and 2 telephone visits. The study will measure liraglutide effects on motor (assessed by changes in the MDS-UPDRS part III) and non-motor symptoms of PD (assessed by the NMSS and MDRS-2) after 52 weeks of treatment. The secondary outcomes include measures of the association between liraglutide's effects on peripheral insulin resistance, PD symptoms and safety. Collection of blood and urine samples will be obtained to monitor drug safety.