So I was very worried before quitting in May last year, since I was already overweight at 218lbs (99kg). On the first few months after doing it, I ballooned up to 233lbs (around 106kg). At that point I was well into obesity, and there were some yellow flags in some exams.
But then my breath came back, and I slowly rediscovered so much stuff that I used to love and smoking had taken away for me. At first it was simply walking and taking the train to work instead of driving, then a little bit of basketball, then came the gym, and so it goes.
18 months after quitting, I now weight 187lbs (85kg, more or less), with a lot more muscle and a lot less fat. I've been working out 3 times per week, while playing soccer one additional day, and basketball on another. My exams are all within normal and healthy ranges, and, tbh, I never felt this good as a smoker.
It might take a while for things to adjust, but it's important to not fall into any illusion that smoking somehow provides some form of benefit in any regard, including weight management.