How can your girlfriend be stopping you? Is she force-feeding you junk food? If she's not prepared to support you in improving your physical and mental health, then she's not the right person for you.

What does the health food have to to with running (the part she's worried about )? Also, looks like you might need to make one more change in your life.

Sounds like she's paranoid that once you're healthier you won't be interested in her anymore and will look for an "upgrade". Even if that's not the case, your girl needs a therapist for thinking it's normal to try to force loved ones to be unhealthy and refuse them to progress in life. It's manipulative and controlling.