A recent study using the data from The Framingham Heart Study found that obesity spreads to friends. While it’s always possible that some unidentified common cause is actually behind the correlation between a friend becoming obese and later becoming obese yourself it seems they were pretty careful. Their analysis seems to take into consideration the fact that obese people might be more likely to befriend each other, any effect from smoking cessation, and effects related to where an individual lives. They even claim to account for the possibility that obesity might result from some common outside event. Of course one should always be wary of possible errors/oversights when evaluating complex statistical claims like this and be aware of the studies limitations¹ but it is at least suggestive of a harmful effect from having fat friends².

In fact one might reasonably explain this result by saying being around fat people creates the perception that being fat is acceptable and reduces the effort people put in to avoid being fat. Maybe not³ but assume it’s true. This would mean that merely seeing fat people on the street or in the store might increase your risk of becoming fat⁴. Sure we might never prove that a casual glance at an obese person harms your health but we might infer it on the same grounds people infer that any secondhand smoke is harmful⁵.

If so should we pass laws limiting the amount of time fat people could be outdoors? Or maybe stop them from eating at fancy restaurants where they might be especially effective in suggesting to other patrons being fat was acceptable? Sure, such laws might marginalize and vilify the obese but isn’t that what we are deliberately doing with smokers and exactly what this hypothesis suggests would improve public health? Of course you might object that smokers can just choose not to smoke fat people can’t just choose to be skinny but this argument doesn’t fly. After all in the broadest sense of the word obese people could choose not to be obese. It’s an indisputable fact that if they sufficiently restricted their calorie intake they would slim down. Now this may be preposterously difficult to do and genetic/developmental factors may put some people substantially more at risk than others but the same could be said for cigarettes.

Of course I don’t really think such laws would be a good idea. But the point is that simpleminded slogans about cigarette smokers hurting your health simply aren’t useful. Nor is it the case that simply finding the practice annoying/disgusting enough since many people find the sight of obese people disgusting. Obviously what we have to do is balance the harms of banning some activity with the harms of allowing it and be consistent about how we draw the line. So while there is a tiny bit of room to claim that the indoor bar/workplace bans on smoking have been justified the idea that the arguments⁶ for various sort of outdoor restrictions that rely on totally non-quantitative claims like these are compelling is just absurd. At the very least a compelling argument for such a law would have to estimate the risk to health posed as well as the amount of inconvenience such a law would incur.