Obesity rate is twice as high amongst nonsmokers

A study published in this week's British Medical Journal shows that nonsmokers are twice as likely to be obese—and three times as likely to be severely obese—than smokers. This is very interesting stuff, because it is is often said that smokers put on weight when they quit cigarettes. It's also said, albeit much less often, that there is some correlation between the decline in smoking and the rise in obesity. This study offers empirical evidence for both.

The connection between smoking and low weight is not much commented on, presumably because anti-smoking campaigners don't want people who are worried about their weight to 'reach for a Lucky instead of a sweet', as the old advertising campaign went. And yes, I've reproduced that advert here to annoy them.

Why, then, would any public health researcher jeopardise their future funding by highlighting this fact? The answer is that they didn't set out to. The study in question looks at obesity's role in creating health inequalities (a cast-iron guarantee for funding). Social class is closely related to mortality and life expectancy is lowest amongst the lowest social classes. Smoking is one reason for that, obesity is another. Between them, as this study shows, these two risk factors account for more than half the difference in life expectancy between the top and bottom rungs of society.

That, in itself, is useful and important information, but in the process of comparing smoking and nonsmoking women (and it was only women in this study), they also show that the difference in obesity rates between smokers and nonsmokers is, frankly, massive.

The graph above (click to enlarge) shows the percentage of women who are overweight and obese according to smoking status and occupational class. As expected, the highest occupational classes (I and II) have a lower rate of obesity than the lowest.

Also as expected, the smokers weigh less than the nonsmokers. What is surprising is the size of the difference. In most cases, rates of obesity are around twice as high for nonsmokers and, across all groups, rates of severe obesity are three times as high.

As the study says:

Severe obesity was more than twice as prevalent among women who had never smoked in the lower occupational classes than in women who had never smoked in the higher occupational classes and about seven times more prevalent than among current smokers in the higher occupational classes.

Another way to look at it is that nonsmokers in the highest social class have a higher rate of obesity (13.3%) than smokers in the lowest social class (13.1%). Rates of severe obesity—which is a condition popularly associated with the underclass—is actually more common amongst the highest class of nonsmoker than the lowest class of smoker. No matter which class you look at, obesity rates are always higher amongst nonsmokers.

To use the standard language of public health, it is true to say that not smoking is a major risk factor for obesity. This, of course, should not be taken as a green light to take up smoking. As the researchers point out, the health risks of smoking are greater than the health risks of obesity. The study shows that the mortality rate rises by around a third for moderately obese people and doubles for severely obese people. By comparison—as the same authors showed in an earlier paper—smoking increases the mortality rate by at least 75%.

I discussed the reasons why smokers tend to be less fat in Chapter 3 of Velvet Glove, Iron Fist. Partly, it is the result of nicotine suppressing appetite and partly it is the act of smoking which takes the mind off food, but mainly it is the physiological effect of nicotine that increases the metabolic rate, particularly during exercise. In his excellent, but sadly out-of-print, book Smoking: The Artificial Passion, David Krogh says that smokers, on average, weight seven pounds less than nonsmokers. Judging by this new study in the BMJ, that is probably an underestimate.

As I see it, there are two useful messages to take home from this study. The first is brought out in the study itself:

[The results] suggest the decline in smoking rates in recent decades may have contributed to the increase in overweight and obesity.

This is worth bearing in mind when you hear anti-smoking-turned-anti-obesity windbags like John Banzhaf rattling on. People like him have, in a real sense, created the problem he professes to be so concerned about. You can, of course, make a rational case for saying that obesity is less of a health problem than smoking, but you won't hear it from him. (One might even frivolously consider that since Big John's so keen to bring in a 'fat tax', there is an easy way to do it—tax nonsmokers. Sure, not all nonsmokers develop obesity-related diseases but then not all smokers get smoking-related diseases. Not all people who drink soda or eat burgers get fat either, but then taxing people on the basis of risk factors to aggregate populations is perfectly acceptable, isn't it John?)

If the suppression of smoking has indeed led to a rise in over-eating, it just goes to prove the golden rule of prohibition: people will always find some unhealthy pleasure to indulge in when other avenues are closed off. If, by some miracle, the war on obesity is won, it will only lead to excessive use of something else. The whole prohibitionist exercise is futile because the desire for pleasure is a zero sum game.

The second point to consider is that since nicotine is an aid to maintaining a healthy weight, why are alleged health campaigners banning products like snus and e-cigarettes which not only get people off cigarettes but could control their weight as well? If smoking and obesity really are the two greatest public health threats of our time, doesn't that make ultra-low risk nicotine products the penicillin of the age?

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