Europeans aren't that far behind in fatness and obesity.

Not only that, but the continent-level statistics aren't useful for much other than scoring Internet points.

State-by-state in the US, obesity varies between 35-50% IIRC.

There are also significant differences by race (black or hispanic highest, white non-hispanic slightly less, and Asian a LOT less).

If we're being honest, Europe has exactly nothing to brag about -- 1 in 5, or 1 in 4 obesity rates are still amazingly high. Just saying "not as high as the US" is a pyrrhic victory.

Britons aren't Europeans anymore!

I've been to a few countries outside of Europe and the US. Obesity and lesser but unhealthy fatness may not be as widespread yet there, but they're not that far behind. Also, what some cultures consider "not fat" isn't actually "not fat." Plenty consider "chubby" to be perfectly normal (and even attractive).

Of course they are, it's part of the European continent. This is like saying citizens of Lichtenstein or Switzerland or Norway aren't Europeans.

Russia is also technically in Europe but a lot of Westerners don't consider Russians Europeans. So I see no reason why continental Europeans could't consider the British as non-Europeans. In fact, there are plenty of Western Europeans that don't even consider Eastern Europe as 'real' Europe.

Russia indeed spans both Europe and Asia but almost all Russians live in the European part and majority of all Russian history and culture happened or is linked to Europe, not Asia. Similarly Turkey technically is also in Europe (small part of Turkish territory) but nobody seriously claims that Turkey is a European country based on this technicality. Another example would be Israel which technically is not in Europe but is considered to be more European than Middle Eastern. So the Brits not being European is not really such an outlandish claim. Especially that there is a growing tendency for 'European' to actually mean 'related to European Union' instead of its original, geographic meaning.