It may all come down to the fact that the most obese country of all English-speaking countries—the United States—also has the biggest voice in the world. It’s like having someone with an oversize influence, who gets seen more and thus emulated more.
The same could be said across those countries that speak English, as the American image, mystique, and visibility can influence the cultural norms. One culture influencing another would be fine if it were only that the people in other countries were just wearing bluejeans, incorporating blues music, utilizing social media technology, and so.
But we have other cultural behaviors that contribute to the highest obesity rates on Earth. When those activities become incorporated right along with T-shirts, Elvis, and Facebook, language becomes the vector of that transmission. So English does not cause the effect you see, but it acts like a facilitator.
It's the window through which the fume of our unhealthy habits escape to the world. It’s the convenient access point for all who speak it. And the outsize influence of American allure is what moves dietary norms in our direction rather than theirs.
In other words: the more other countries look to us, the more they look like us.
If you live in one of these other countries, remember the cultural habits you had when you were thinner and healthier: fewer processed food products, drive-thrus, and habits like eating on the run. Reincorporate more traditional habits before adopting the eating norms of a country in which two-thirds of the people are overweight, obese, and morbidly obese.