The lack of a strong, centuries-lasting food tradition is what makes the US such an interesting country in which to eat food at the moment. Alas, it is also the main reason why Americans seem to be so prone to fads, including diet fads.
French and Italians cuisines have all formed during centuries, assimilating traditions coming from different influences. On the bad side of things, this means they are now less open to new things, and they may be described as stiff. (Spanish cuisine is probably the exception here, with its capability to innovate itself profoundly at the moment). Because "American cuisine" is so new, Americans are more eager to try new things: some of them work, some don't, but at least this process of trial and error can generate new things.
The problem is that this lack of a stable dietary history also generates diet fads. The level at which the average American person seems to be influenced by diet fads is incredible. Up until 2002 the official government's guidelines invited Americans to eat grains and carbs and to reduce the level of animal fat. At the same time though, the Atkins diet was all the rage with a vast sector of the population, advocating exactly the opposite: cut the carbs, increase the fat (including animal fat) and eat as much of that as you want.
The low carb histeria exploded thanks to a famous article from the New York Times, appeared in July 2002. It cast a doubt over whether fat was really the culprit for the overweight pandemic that had struck America since the mid-70s. Overnight, a country which had been taught to eat pasta like Italians do, because it was supposed to be good for you, started to obsess with low-carbs options. I distinctively remember spending New Year's Eve in New York in 2002, and every waiter was offering low-carb options. I didn't even know what it meant at the time.
Now there is a new fad coming along: the so called paleo diet, which actually originated in Europe. It advocates for a regimen based on what we think paleolithic men were eating, from 2.5 million to 10,000 years ago, before agriculture came into the picture: lots of meat, no pasta, no bread, no grains (all agricultural products or byproducts). The theory behind this actually doesn't sound too wacky as you might think: their point is that from an evolutionary point of view, man evolved to consume meat, roots and berries. Agriculture appeared too late in the game to have had any impact on our evolution as a species yet. To imitate the paleolithic lifestyle, there are even those who fast for 36 hours, exercise with an empty stomach, and then eat an entire buffalo. And I am not even joking, people.
As for me, I simply don't trust nutritionists. As the fat/carb issue well proves, nutritionists are always ready to crucify you for something, and then the day after they will be on your back for something else.
And tonight I am eating pie.