UK here, I can't really say to be honest. Fatties most likely go to Tesco which is our version of Walmart (all dominating supermarket empire). There's a store called Lidl which is derogatively seen as the place for poor people to shop at, but the reality is there's actually good quality meat from these stores.  I would wager that you wouldn't see many fat asses at Marks and Spencer, that's more pricey for middle/upper classed people.