Does Walmart make you fat?

Why might people in developed countries be eating more today than they used to? One plausible factor is the fall in the cost of obtaining food. Hunting and gathering is such a hassle in comparison with going to the supermarket. Going to the supermarket entails a lower risk of being mauled by a bear or getting caught in a gorse bush, for example. You could say that going to the supermarket is more calorie-efficient compared to hunting and gathering: i.e. you use fewer calories relative to calories gained. (Not to mention the absence of any need for serious protective clothing – I mean, pyjamas aren’t really ideal hunting and gathering wear, but they will do well enough for a trip to the shops.)

So, might lower food costs result in higher food consumption? Economists Charles Coutemanche and Arte Carden investigated how Walmart’s lower food prices might be contributing to obesity levels in the US. In particular they looked at whether the opening of a new Walmart superstore in an area caused increased levels of obesity.

As is almost always the case when analysing economic data, identifying causality is difficult. Could Walmart be picking out areas that are likely to be the most profitable, because people in those areas like cheap food and tend to be obese? The authors try to control for this using the fact that Walmart expanded geographically from its headquarters in Arkansas – luckily a strategy that is unlikely to be linked with obesity levels in different areas.

According to the study, “an additional Supercenter per 100,000 residents increases average BMI by 0.24 units and the obesity rate by 2.3 percentage points. These results imply that the proliferation of Walmart Supercenters explains 10.5% of the rise in obesity since the late 1980s”.

Quite an achievement.

The study does however suggest that the cost that Walmart imposes in terms of obesity is outweighed by the benefits of cheaper food. Well that’s alright then.

Walmart: Save money. Live better (but slightly tubbier)

The paper is here.

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