There are several factors that contribute to obesity, one of the prominent ones is walkability. With the second world countries, having more space in general, they lack the environment that promotes walkability. These countries are well equipped with parks but they lack the facility for easy commute. One of the articles below shows the influence of walkability on the obesogenic environment.
The above maps compare the number of intersections in a European city vs Los Angeles and also Irvine, CA. Irvine is a city that is lush with many parks but unfortunately, it does not help people who could commute to places through walking.
This is an eye opener for city planners as such as a challenge for them to try to reduce obesogenic environment which would fit other lifestyle choices.