You can walk. If you are at 50 + lbs of weight and haven't run at all fast walking will put you in the same cardio zone as running for a lighter weight runner. The math of calorie loss as it goes with running is the simple equation of how much weight are you moving and what cardio zone is your body operating in to move that weight. If you can hit low aerobic fast walking (most non runners can do that easily), just do that.

Beyond that I am not sure about how running impacts the joints of heavily overweight people. I would advise a very slow and conservative ramp of up mileage. I think as long as the body is given time to adjust it can do so with minimal risk of serious injury (even if you are running). The problem with running is your aerobic capacity will likely outstrip the rest of your bodies ability to absorb punishment. This is why so many "I am going to run a Marthon, but have no prior running experience" people end up injured and then wander about telling people how bad running is for your joints, etc.

(https://www.runnersworld.com/general-interest/runners-have-m...). Could just be a self reporting bias, but it is interesting. Several studies over the years have looked at life long runners knees and they seem to be fine compared to a non runners.

I didn't even go into some of those "soft" benefits of regular exercise, such as the mental boost it gives (which seems like it would support weight loss), along with the obligatory lymph system circulation which is likely to improve immune health and help with waste cycling. As long as someone isn't overtraining, that is :)