Even tough both western and eastern diets are based on similar foods, the amounts that these foods are consumed at is completely different from one diet to the other. Its all in the amounts and importance of certain foods above others that makes the difference between the two.
The thing that demonstrates the difference mostly is the food pyramids. In the eastern pyramid, they eat rather small dishes that mostly comprised from rice and greens, as opposed to the western menu which mostly contain meat and the dishes are quite large.
Regardless of the activity levels, a decadent way of life combined with a greasy diet would surely lead to poor health. Eastern cultures who only pursue semi-active lifestyle but maintain a healthy diet would most likely have a larger lifespan.
We can all take example from Japan – even though they have experienced a boom in the fast food market, the choices made and food preparation has maintained inline with the plant based diet of their historical foundations.