smoking as weight management

Someone who has been a smoker for about 20 years claims she won’t quit because she’s afraid doing so will cause her to gain weight. Apparently the side effects of looking older than one’s age, stained fingernails, not too mention the damage to the lungs and cost aren’t important. What matters is not gaining a few kilos. I’m sure there’s a logic to this way of thinking, I just haven’t found it…