And if you are overweight and sedentary DON'T RUN TO GET INTO SHAPE.
Walking, hiking, swimming, biking, and weight training. Mix all of it so you get cross training effects and distribute stress across many domains.
Running is, by the standards of the statistical hole America is in terms of obesity, an "advanced" activity. We're talking about something that involves a stress increase of 2.5x to 4.x over walking.
Now consider that an obese person with an extra 50 lbs of fat is on their body. Running will be an extra 200 lbs of stress on your feet, and none of that fat tissue is absorbing impact or stabilizing that impact. And on top of it, the fat will disrupt the neuro-biomechanical flow of your neuromuscular system, making you less coordinated and therefore also harder to absorb the impact.
As I said elsewhere: use GLP-1 to get the fat down and simultaneously employ a gentle ROUTINE activity program that morphs into more and more exercise and exercise variety.