It is just my very biased opinion but Brits' diet seems to be one of the causes of why so many Britons dying sooner than expected [0]. The average Londoner eats rather poorly. So many greasy sandwiches and crisps, even their salads have to be all greased up in ways that would make my grandmother cry. Fish and seafood are seen as a "chic experience". Copious amounts of beer. And then all the snacks, munching on stuff the entire day (it says "healthy" in the package so it's good right?). Are we cows to be ruminating all day long? They're not even good snacks like some nuts or whatever. Massive breakfast, then a mid morning break for "coffee" (it's just milk and sugar), then lunch (sandwiches or salads filled with sauces), then midafternoon snack then several pints of lager after work and a dinner to finish the day. It's a lot of calories, and lot of bad nutrients. No wonder so many people are obese, if you don't have a very active lifestyle it's easy to get really fat.
By no means I'm saying my country is perfect, I see there people moving further and further away from what our ancestors usually ate and it shows on obesity rate is increasing, kids are getting more diabetes diagnosis and so on. But here in the UK it's just too much, a walk through Tesco makes me cringe.