There are quite significant differences among different European countries. During every doctor's visit in England I was told that I was underweight and needed to gain weight, but I wasn't skinny at the time. One of my Japanese flatmates was considered "chubby" by Japanese standards and English doctors told her to gain weight too! She was neither chubby nor skinny in my eyes! I had problems finding clothes in England too, I actually had to find my trousers in Germany because they just never had my size.
Right now I'm actually in a situation where I can't gain weight because of a diet I need to follow due to various health problems - a variation of the paleo diet. It's incredibly difficult to gain weight on a diet that cuts out all processed food and sugar, and reduces starch to the bare minimum (pumpkin yes, potatoes no). Basically when you eat only "real food" - Meat, fish, fruit, veg, eggs - it's almost impossible to be overweight unless your hormones are shot or you eat a packet of nuts every day. And that kind of diet is basically the opposite of the standard american diet with mostly processed ready meals and double to triple the amount of sugar in desserts and soft drinks. When my dad used to exchange cake recipes with his American friends he always cut the sugar by at least half, otherwise it was inedible for our European tastes!
The English diet is closer to the American diet and consists of a lot of ready meals and "cooking" usually means to put some ready meal in the oven. It was rather practical for me while I had English flatmates, because I was the only one who really used the kitchen. English cooking is actually known in the rest of Europe for being particularly bad. During language school trips in my teenage years I was served the most atrocious things by host families, apart from the one time I was really lucky and had a chef as the host father
By the way, even within one country there can be a noticeable difference. When I moved from East Germany to West Germany everyone seemed fat to me in the beginning. They eat at restaurants and Turkish fast food places a lot more there due to longer commutes. Compared to England vs Germany the difference is negligible though. Spain and Germany is roughly the same, people cook a lot here as well, probably more than in Germany actually.
In Eastern European countries there is usually an age difference. Young people tend to be slender and then fill out a lot when they are older. The women from the village where my mum grew up used to tell her to "finally find a man and gain some weight". They eat a lot of heavy foods with lots of starch, lots of meat and cook with a lot of oil too. Vegetables other than root vegetables seem to be an afterthought and aren't always available depending on the season.
So, even though Europeans are generally thinner, there is quite some variety among the diets. Germans eat a lot of dark bread and variations of meat / sausage, Italians a lot of pasta and pizza, English people ready meals and Indian food, Spanish people more fish, meat and fresh produce, Eastern Europeans potatoes and meat. You first have to pick a country to "do as the Romans do".
I don't find this thread so weird. What people eat has a huge impact on the culture, the times of the day when they eat and so on. One example: Spanish people tend to eat a heavy meal at lunch time and then lie down to sleep a siesta. This means that from 1.30pm - 5pm any Spanish town will be dead and most shops are closed. The climate usually also means that people come out onto the street mostly in the evening and stay out with their kids until late at night, especially in summer. You will see kids on the street until 11 or 12, sometimes even later. In Germany people send their kids to bed really early and when you keep your kid up and outside beyond 9pm random strangers might shout at you for mistreating your children! The whole rhythm of life is different and it took me about 2 years to adjust to it.