There is a type of seaweed that if your average American eats it, there are zero calories absorbed.
If most Japanese citizens eat it, they will absorb calories from it.
There is a gut bacteria common in the Japanese population that extracts calories from this type of seaweed.
"calories in" is that calories that went down your throat. It is calories that your body was able to digest, and "your body" includes many types of bacteria that are unique to each person and also unique to different population groups (meaning that some populations share commonalities in gut flora).
It is possible that certain antibiotics have wipe out some types of gut flora, allowing others to proliferate more. That alone could increase calorie absorption. (Or cause a host of other problems!)
It is possible that having a diet too heavily reliant upon one type of food results in an imbalance of some type. The problem is, this is a brand new area of research and we just don't know yet.
But it is sure as heck known that it is more complicated than "calories in food down the throat".
This sounds incredibly interesting, and I would like to know more about this. You wouldn't happen to know the name of the seaweed or have a link to a study, would you?
Actual suspected caloric difference is minimal, after all, well, it is seaweed, not a very dense food stuff. :)
I'm not going to link to antibiotics causing gut flora problems, it is well known and responsible doctors actually can prescribe a nice little compact pill full of gut bacteria that replaces the ones wiped out as a side effect of antibiotics.
The stuff about a biased diet messing up gut bacteria is also hard to find research on (I've read it, but it is a PITA to find again). Basically different bacteria specialize in breaking down different types of food. If you have a diet lacking in some major food group, that stock of bacteria runs low.
Vegans can have this issue if they go back to eating meat. There is typically some tiny supply of the needed bacteria left and the population is restored after awhile, but the initial few hamburgers can be somewhat uncomfortable.
I'm betting that increased use of antibiotics is a key factor. Antibiotics are used in livestock management to increase feed efficiency. And young adults today have taken far more antibiotics than young adults had done in the 60s. So they use food more efficiently.
If most Japanese citizens eat it, they will absorb calories from it.
There is a gut bacteria common in the Japanese population that extracts calories from this type of seaweed.
"calories in" is that calories that went down your throat. It is calories that your body was able to digest, and "your body" includes many types of bacteria that are unique to each person and also unique to different population groups (meaning that some populations share commonalities in gut flora).
It is possible that certain antibiotics have wipe out some types of gut flora, allowing others to proliferate more. That alone could increase calorie absorption. (Or cause a host of other problems!)
It is possible that having a diet too heavily reliant upon one type of food results in an imbalance of some type. The problem is, this is a brand new area of research and we just don't know yet.
But it is sure as heck known that it is more complicated than "calories in food down the throat".