Im from Scotland but live in Switzerland and I have lived in or visit countries such as France, Italy, Spain and Germany quite often.
There is nothing surprising in these results for me, considering what you see in each country.
For me, the biggest factors are
Exercise
The UK has adopted the American way of driving everywhere, even a few hundred metres and barely walking, this is made even worse as, due to the nationwide kiddy-snatcher paranoia of the last 20 years, kids arent even walking to school anymore, theyre driven or get taxis whereas when I was a kid, youd walk the mile to school each day.
In Switzerland, everyone has a bicycle, even old people, people dont drive short distances, they cycle and walk much more.
They also do more sport, you see people heading off to hike in the mountains or jogging much more.
Food
Its not about fat, its about sugar and processed food.
In the US and UK people eat a lot more processed food in terms of ready meals and stuff like that, frozen dinners etc., theyre eating stuff thats loaded with salt, sugar, flavour enhancers and other crap.
Eating freshly cooked, real food would make a large difference.
In the US, the portion sizes in restaurants are obscene, often double or more than what youd find in Europe, theres no need for it whatsoever.
Drink
In the UK they drink more alcohol, especially beer than in countries such as Italy and Switzerland, it doesnt help.
The soft drink consumption in the states is basically sick, those massive buckets you can get are totally unnecessary.