If you’re a smoker who’s ever expressed concern about gaining weight if you quit, you may have encountered the “rule of thirds” somewhere along the line. The smoking cessation rule of thirds says, essentially, that around a third of quitters gain weight, a third remain the same, and a third actually lose weight.
This pat formula cropped up a few decades ago and no one can say exactly where it came from. Presumably the first person to utter these words meant well and hoped to encourage his (her?) smoking patients to overcome their reluctance to quit because they feared gaining weight. After all, what could be more reassuring than the idea that your chance of gaining weight is only a little over 30% – with an equally good chance that you’ll actually lose weight?
Only one problem: It simply isn’t true. There is no scientific evidence whatsoever to support this breakdown and plenty to refute it. Only a few quitters completely avoid weight gain and even fewer actually lose weight. And I’m convinced that many of those who lose weight have cessation-emergent depression and concomitant loss of appetite, a poor tradeoff! Yet somewhere along the line the rule of thirds became so entrenched that now, even when its “untruthiness” is pretty widely recognized in the research community, it still turns up occasionally, like a bad penny.
What’s wrong with a little white lie if it has the desired effect?
Plenty, in my opinion. Because weight gain often begins as early as the first week after quitting, this particular piece of disinformation is likely to convince women, before their attempt to quit has even gotten off the ground, that they’re in the unlucky third, that they’ve lost the lottery. It’s hard to think of a better formula for early relapse!
The precise distribution of weight gain after quitting is not easy to specify because of methodological issues (e.g., how long after quitting do you measure? how do you factor in normal weight gain over time in nonsmokers? etc.). Based on my own reading of the literature, however, I have developed my own algorithm that I think is a lot closer to the truth:
What does this mean for you? Readers of Life After Cigarettes or of this blog will be well aware of my conviction that it is likely, by definition, that you will be among the large majority of women smokers who do not gain weight in amounts that will require a new wardrobe or increase your health risk when you quit.
The other thing to remember is that whether you will be among those who gain weight in disproportionate amounts is not entirely a matter of chance. There are risk factors for large weight gain, including a history of binge-eating, a personal or family history of large weight gain after previous quit attempts, and a tendency towards depression-induced eating. Having one or more risk factors for excessive weight gain does not mean you shouldn’t quit smoking! It does mean that you should consider taking precautionary measures to counteract these propensities (e.g., using smoking cessation medications that minimize weight gain, such as nicotine replacement therapy or Zyban; reviewing your nutritional and exercise patterns with an eye to identifying realistic changes you can make) and be prepared to seek professional help if weight gain after quitting gets out of hand. Whatever you do, please don’t quit quitting!
Cynthia S. Pomerleau, Ph.D., is currently research professor emerita in the University of Michigan Department of Psychiatry. From 1985 to 2009 she served as director of the Nicotine Research Laboratory, where much of her research focused on the impact of smoking on women. She is the author of more than a hundred articles and book chapters on smoking and a contributor to the 2001 Surgeon General’s Report on Women and Smoking.