My weight remained stable after I started vaping. Then, about 18 months in, my doctor advised me to lose 30 pounds. I lost 40 pounds instead, and it was no problem. I've kept the weight off, too, with very little effort on my part.
By contrast, I've known a lot of smokers who quit cold-turkey and consequently ballooned, some gaining a hundred pounds or more. These poor people then try to diet and are ultimately unsuccessful at keeping off the weight. As they've aged, they've become prone to obesity-related health problems.
I wonder if there's ever been a study done of life expectancy and causes of death for those who continue to smoke right up until they assume room temperature versus those who had quit smoking decades earlier.