Yeah, American English vs British English can be a fun one - I'm fluent in both (well, most of the time, anyway!) after living in the UK for 16.5 years. What gets difficult at times is when there are things for which I first learned a word in the UK, then struggle with figuring out the American equivalent.
I suggested to my dad once that he get a waterbutt for his house downspouts. He's like "what?" I'm struggling because I have no idea what else to call it... "oh! You mean a rain barrel!" yeah... :-p
Then, some of my fiction, I first wrote when I was using British English all the time. So, I had to actively decide which English I was going to use most of the time... American makes the most sense for me, but I will regularly use some Britishisms too - such as "corridor" and "canteen" (instead of cafeteria).
Fine to pass on religion - definitely a minefield...
On nutrition, I remember noticing that the food guidelines were based on more and more carbs/grains and people were getting fatter and fatter... and not for lack of trying on the part of many! In fact, I sat down and counted up typical calories recommended in one of the food pyramids and found it exceeded what they wanted us to be eating - they might have changed that one though. :-p
Another health one...
I believed the doctor who told me I'd have an underactive thyroid for the rest of my life. WRONG! I've corrected it now and have kept it that way for the past 8 years!
Ah lol, waterbutt! What is the American equivalent of corridor? Is it hallway?
Calorie counts for food is also a idea that is being reinvestigated. It is currently a measure of the chemical energy released by combustion. Hoever, we don't really operate with a furnace in our stomach, so the actual energy absorbed is somewhat different, depending on the food and the combinations of food. Ahhhh, biology, such a messy and horribly inelegant field...
Yes, a corridor becomes a hallway - or simply a hall.
And yes, you are totally right. Calories in - calories out equals weight loss or weight gain - as a model it is grossly incorrect. I have met people larger than my obese body who cannot lose weight no matter how little they eat or how much of the USDA-type model they ate - and this was in the UK as well! The system is broken because the whole model is broken. We need to eat more like what our ancestors ate - and without all the pesticides sprayed all over the place.
I've heard of people who are gluten intolerant, then they go to South America and eat the bread there - they are FINE!!! I now understand that it is highly likely that even that wheat isn't very good for us - that there have been records of gluten intolerance in pre-bibilical times, but we, as a people/species managed to do "okay" for a very long time, then you got modern techniques in there, more or less changing the type of wheat we eat, sprayed with crap - and we're not even at GMO status with grains yet - and suddenly there is a very large problem! (both numbers and size.)
I used to joke when in the UK and people would ask me what it was like in the US... "bigger - everything is bigger, the cars, the roads, the people..." but it's definitely no joke that our modern diet is killing us!
< / soapbox >
lol