I'm an American expatriate living now in Japan. This is a question I've asked myself a lot, as whenever I travel between the two countries I am always reminded at the stark differences in average body shapes between the two countries.

Like others, I think the primary physical cause is portion size. When I first came to Japan, having been raised my entire life on super-size everything with free refills, I was pretty annoyed at how everything was so small. In time, I came to realize that these "small" portion sizes were actually quite reasonable and satisfying when the quality of the food was nutritionally high, and it is the USA which is actually a bit unusual in its gargantuan portioning of almost anything food related.

Now comes the real question... why are American portions so huge? This is the root of the issue I believe and it extends not only into food quantities, but also lifestyle choices. If you look at American home sizes, they have also been getting much more grandiose and luxurious... and there seems to be a race towards getting all of middle-class America to live in a McMansion of their own. This, again, is in stark contrast to the average Japanese sense of home, which is much smaller and much more focused on efficiency and practical living than it is on projecting an heir of luxuriousness and grandiosity.

I'm sure there are any number of potential reasons why the average mindset in the USA is stuck on 'bigger is better'. There are probably many lengthy, intellectual treatises written on the subject, which I don't really want to delve into for a simple message board post. But I think that if America can switch its habitual thinking to something more along the lines of being genuinely satisfied with what you currently have instead of feeling empty and feeling like you always need something bigger or better, it would go a long way to curbing the obesity problem as well as some of the issues with rampant greed that seem to be plaguing a lot of the society.

Maybe because the American cuisine is, well, disgusting. At least, from a point of view of someone accustomed to one of the world's best cooking environments (Campania, Italy, mozzarella di bufala, cucina mediterranea etc.)

XD Good point but then what about the English? While Italy and France rank up at the top in terms of fine dining, the Americans and English tend to just boil fry and eat. :P

It's not a rule. There are many americans that are perfectly fit. Still, the diet part plays a huge role into what bodytype you end up with.

1) American breakfast, at least as we learned it at cooking school, is very big, contains MANY things, and is made of harmful things, much like omelets, sausages, cheese, bacon and other fatty and unhealthy food items. But omelets and sausages usually are fried in the pan; 2) Deep Fry and 3) deep freeze, are the most unhealthy and fattening cooking procedure and preservation method, respectively.

4) Then, we have burgers. Homemade burgers that are not very loaded, especially with sauce/cheese etc, can be good for you (or not very harmful at best), but when you eat them on those horrible fast food restaurants, like MacDonalds, it is like smoking bad quality cigarettes; slow suicide!

Then, we have the 5) french fries, those that are following main food, as fried. They are deep frozen, get deep fried, and are full of chemicals/unhealthy preservatives, like that clouding powder inside a McKain potato bag, red in color, which transforms part of the potatoes' surface into a sickly green color. Guess what; we are eating chemistry, people!

6) Genetically mutated food. Stuff should be banned. Some of those have the decency to write upon them the fact that they are genetically processed; many of those, will never. You eat a genetic monstrosity while thinking you are enjoying a biological product of high quality (bleargh)! This thing is very dangerous, despite the struggle of certain people and corporations to prove otherwise. Avoid it like hell.

7) Seafood. Seafood coming from clear waters, is like the stuff of heavens, especially when FRESH and properly prepared. On the other hand, seafood that comes from areas that have petrol oil leakages, nuclear tests taking place nearby (hello pacific and tiny islands!), or are frequented trade routes and ship passages, even worse shorelines near industrial areas and heavily populated cities, well, you can imagine where all that waste ends up to. Right BACK into your peptic system, after paying a short visit into those poor marine animals' body.

8) Peanut butter. Replace with HONEY. This is a killer. Very tasty and yummy, but very fat and fattening. And imagine that after cocoa/chocolate, it is the second food highest in containing bug, yes, bug parts... Some people avoid fat altogether, even hazelnut spread or normal butter, and they do well to. Fat can be good and bad. You can do a small research about useful fat and harmful, in food, i do not present everything because it will be too long. And remember, tasty doesn't equal healthy. Actually, normally, the more tasty something is, the more unhealthy it can be for you and your body.

9) Cola. Damn, that is the stuff of damnation. One small glass of it, contains 2 times the daily quantity of sugar your body needs to work well. This and soda, as well as most refreshments that are NOT natural juice, can transform even a hardcore athlete into a fatash fattard, especially when abused. Try some natural juice before stocking up on these chemicals, they are way yummier and healthier. And they still possess vitamins that your body needs and can use, unlike the industrialized devils aforementioned.

10) Chemically processed items to augment your diet; energy drinks, supplements, coffee in tins from vending machines, etc. This is poison. Even the drugs made for athletes. You need supplements, correct, everyone does. Try some vitamin rich natural juice, or something. Maybe bee products. (fresh) Bee pollen for example can help in developing muscle mass, you do not need pills and raw protein. Royal jelly can augment physical condition, reflexes, body performance overall, etc. The less processed the ingested food is, the better absorbed and utilized by your body it becomes! Instead of coffee, you could get a ginseng tea or tincture, with similar and even greater results (keeping you awake and full of energy).

11) Instead of sweets, try out fruit and natural sweeteners! You are going to be impressed.

12) Last but not least, physical exercise, even if only typical, light etc. You do not need to overexert yourself, just to keep in touch once in a while. Yes, even the "infamous" one can be extremely beneficial and rewarding, both in mind and body. And as i read from statistics, americans "do not keep traditions", as of late...

I am not reproducing stereotypes. I do not want to sound nasty or offensive, and sorry if i do. That is what i think i know, and my humble opinion is not airheaded, but the outcome of studies (culinary arts), which, admittedly, might be outdated, too. I want to help people against fat. I myself had been 105 kilos once and borderline obese, now i am 80 and with a very fit bodytype. Remember, though, many sacrifices are needed and it does not have a shortcut or easy way to do.

Just perception, like "all you can eat" buffets etc.

I remember a buddy of mine went to Florida, in a steak restaurant the steak dishes were huge and if you managed to eat it all, you didn't have to pay.

I think restaurants try to offer more product for less money to entice customers, which leads to over consumption.

*Note to self : Must watch that Supersize Me movie.

You are quite right. My bad.
https://www.cia.gov/library/publications/the-world-factbook/rankorder/2228rank.html

As we can see here USA is on 18th place, while China only on 152. Hooray! :)

There are plenty of fat people here too. Only without so much excuse when it comes to things like an unregulated food industry, super sized portions and fast food being the cheapest option (here it costs a lot more than something you can make yourself).

For reasons of political correctness in the UK we have to recognize that fat people have made lifestyle choice and we are obliged to only refer to them by the PC term 'lardarse'.

Best politically correct term I've ever heard in my life ;)

There's a cultural factor here, too. The Japanese are ethnically unusually homogeneous, for one thing, and their culture is more communal than the highly individualistic American one: since the Shogunate was ousted from power (the post-WWII restoration is another focal point if you need one), Japanese individuals and businesses were encouraged to aspire towards the common good rather than climb their way to the top. The concept of face is strong in Japanese culture, too, so broadly generalized, it would be humiliating to admit that you are having trouble getting by with your salary; and on the other hand, it would be very rude and ostentatious towards those same neighbours if you were making piles of cash and overtly showed it.

And don't forget having the honor of having the highest suicide rate amongst developed nations. Sacrificing for the greater good can sometimes end up with an open stomach... seppuku style. Be careful what you wish for.

Because US is the true heaven of fast food market and Americans love ff very much.

Utter misconceptions about distances and speed or an irrational hate for walking. No, really, I keep noticing it when I watch American movies and shows. In HIMYM for example. In the last season there's a scene where Marshall's bus breaks down and he decides to do a CRAZY thing. WALK! How far? FIVE MILES! FIVE FRIGGIN' MILES! OMG! THAT MADMAN! I mean seriously, that scene is supposed to be funny because he clearly overestimates his endurance or underestimates the distance or something. What the heck?! Five miles is roughly the distance my parents walk on their afternoon walks almost every day, it's the distance I jogged with my buddy regularly (and I've never been close to being an athletic guy). And in another show (don't remember which one) I saw a scene rather recently where a guy considers to go on foot and another fella goes like "you crazy? it's two bus stops!". I don't know if bus stops are further apart in American cities but in Europe that's like five to ten minutes on foot! And I keep seeing this stuff all the time so I presume that there's some truth to it. Seems like some really weird cultural phenomenon that makes you guys walk too little. I'd blame the imperial system but it's not exclusive to the US.

Btw, funnily enough also a guy from the German military I know observed a weird thing related to that matter. They marched with American soldiers once. The US soldiers were pretty muscular, some of them like REALLY buffed, the guy said that he and some his comrades were quite intimidated by them. And then they marched. And all the US soldiers were exhausted when things just had started. The Germans with their average appearance, some of them even being chubby, were just getting warm when nearly all the Americans were close to collapsing. Now I know that being buffed doesn't say much about one's endurance but come on. Anyway, it further confirmed my presumption that Americans, even seemingly athletic ones, just don't friggin' move enough. And I wouldn't be surprised if that were somehow related to why the average american is comparably fat.

That's true but in turn "we"(the west) have a higher crime rate, so anger is directed towards others than towards ourselves. And no, I'm not saying that this is better in any way, both things are bad.
I have yet to find the perfect system, every system/society is lacking in its own unique ways.

Oh, on top I'm not perfect either, basically no human is. So I guess we found the reason why we're always working towards our doom.

It's the quality of "food" (I don't actually call a lot of it real food, which is why I use quotes.) More specifically:

Genetically Modified ingredients, artificial colors+flavors, and chemical preservatives/derivatives/additives.

Combine that with the majority of the population being HIGHLY under-educated as well as systematically "taught" to be lazy and impatient (easier is better mentality.)

Combine that with the mentality of invulnerability and that modern medicine can fix all of your ails. Most people in the US are of a band-aid mentality rather than a preventative mentality.

Combine that with a lack of accountability to self or responsibility to the earth or future generations (parents don't care to feed their children healthily or live in a way that makes the world a better place for future generations.) The majority of people in the states support an unsustainable, greed-driven system of agriculture.

All of these problems bleed into each other/perpetuate each other.

I could certainly elaborate more.

There is no perfect system. Never has been, never will be. Why? Because it has and will always be created by imperfect beings. But we need a reason to move forward. Nations, tribes, leaders, ideas, money, land, power, whatever. The outer party is usually as corrupt as the inner party. Whether we're using rifles, swords, or nukes, the only thing that seems to unite us all is our ability and desire to harm one another. Sad legacy.