>>I regularly travel to Japan

Lucky you! I've a Japanese born (Hokkaido) friend here on the East coast. He's married to a US born woman. Their kids are all bilingual (Mom spoke English to them, Dad Japanese, even though they both spoke both languages). They grew up here in the US, were not at all overweight - and did not eat a standard American diet (best as I can tell, it was kind of a Japanese-Medeterranean mash up - and I never saw soda in their house).

If there's a dietary "worst thing" we're doing, it's soda. I've been watching the 'obesity epidemic' spread across the world, following in the trail of those sugary drinks.