In this Santa Barbara Independent article, there is an interesting explanation of why French don’t get fat whereas "they eat three times as much saturated animal fat as Americans do." The article author Michael Seabaugh quotes  Laurence Hauben an expert on the subject:

“The French don’t traditionally wolf down a meal at their desk or while commuting in traffic,” she said. “They sit down with family or colleagues at a table, taking the time to relax and share conversation. When you are talking, you are not eating, and because you are relaxed, the hormones released help in the assimilation of calories, unlike the stress hormones we are riddled with here, which trigger hoarding of fat. In other words, eat 800 calories while sitting at a café in Paris, and they will get spent. Eat 800 calories while sitting in your car in traffic on the freeway, and most of them will settle in your hips or gut.”

Found via DMiessler.