They probably have cultures of smaller portions, less processed food, and less a...

They probably have cultures of smaller portions, less processed food, and less added sugar (especially drinks). Example: compare the size of a Japanese mosburger with a burger & fries meal in the US:

http://www.thetraveltester.com/wp-content/uploads/mos-burger...

When you meet foreign travelers, ask them what they think about US serving sizes. Many of them find it shocking.