Brittany, a 27-year-old woman living in New York City, is unhappy with her life. She works a dead-end job at a theater and spends her free time partying and drinking. After a visit to the doctor, she realizes she needs to make some changes to her lifestyle. Inspired by her neighbor Catherine, who runs every day, Brittany decides to start training for the New York City Marathon.
At the beginning of her training, Brittany struggles to run even a single mile. She also faces obstacles such as her own negative self-talk and criticism from others who doubt that she can complete the marathon. However, as she continues to work hard and make progress, she gains confidence and a new sense of purpose.
Brittany's training journey also leads her to new friendships, including a fellow runner named Seth and a woman named Jern, who is dealing with her own personal struggles. Along with their support, Brittany also receives help from a personal trainer named Demetrius, who encourages her to push herself and stay committed to her goals.
As Brittany trains for the marathon, she also confronts the underlying issues that have been holding her back in life. She reconciles with her estranged father and breaks off a toxic relationship with a man named Ryan. In the end, Brittany completes the marathon and feels a sense of pride and accomplishment that she never thought was possible.
Overall, Brittany Runs a Marathon is a heartwarming and inspiring film about the power of determination, perseverance, and self-love.