Last year, some friends and I went for dinner at Brouwer's Café, a Belgian pub/restaurant in the Fremont neighborhood of Seattle. The menu is pub food, which means that everything comes with frites and a choice of several dipping sauces, none of which is ketchup. One of my friends spent some formative years of her life in the Netherlands, so she was familiar with frites and asked for curry ketchup. Unfortunately, they didn't have it. (But I know a great German deli that does carry curry ketchup...)
I tried to stay somewhat healthy with a salad, but the croque monsieur pretty much cancelled out any fat-avoidance forgoing the frites may have offered. As we munched on our frites, I wondered how the Belgians managed to eat such profoundly fatty food and not blimp up like Americans. My friends revealed the secret in one word: nicotine.