Quitting and weight gain

Do people really put on weight when they stop smoking, or is it just something we say? 

It's not necessarily true, depiste what most people think. A third of smokers don't put on any weight when they give up, while others put on 2-4 kilos, which is negligible. You need to consider that smoking disrupts your bodily functions, so many smokers are lighter than they would be if they didn't smoke (2.8kg for men, 3.8kg for women). But still, we're not talking about putting on 10 kilos, so don't get worked up over a weight gain of 3 kilos, especially weighed up against the benefits of quitting smoking.