Let's be clear here: if you buy unhealthy foods from any supermarket, you'll end up gaining weight. But an intriguing study in Europe suggests that people who shop at cheaper supermarkets might be more susceptible to weight gain.
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A study conducted in Paris in 2007 and 2008 and including 7,131 participants found that body mass index (BMI) and waist measurements were higher for participants who shopped at discount supermarkets, had low levels of education, or who used supermarkets a considerable distance from their own neighbourhood. (As we've mentioned before, BMI isn't necessarily a good measure of individual health, but is widely used when comparing groups.)
It's only one study, and the supermarket landscape varies a lot from country to country. Australia and France both have ALDI, for instance, but they're actually run by different organisations; Australia is ultimately part of ALDI Sud, France is run by ALDI Nord. And Paris' urban density is quite different to that found in Australian cities. The study found that only 11.4 per cent of participants primarily shopped in their local neighbourhood; it would be interesting to see comparable numbers for Australia.
It's also clear that the demographics involved are important: discount supermarkets are often located in less affluent areas, the effect was more marked amongst lower-educated participants. So if there's a lesson you can definitely draw, it's that spending time to think about your food choices always pays off.