I've known a few heavy pot smokers, I would say over time they get fat and unhealthy because all they do is sit down and eat, they don't exercise and this leads to other health problems.
I'm 62 years old, 5'7" tall and weigh 160 pounds get lots of exercise eat healthy and smoke about a pack of cigarettes about every 4 days. But everybody is different and some people have an unhealthy life style which is their choice regardless if they smoke Cannabis or not. Again high THC content with very little CBD can make one isolate themselves where CBD has the opposite effect.