Not really. More and more people know how to avoid getting fat, thanks to the internet. I'm 21 years old in a western European country and barely anyone my age is overweight, and a sizable minority even has a professional athletes body from working out.

Which country is this? France or one of the Scandinavian countries?

"New WHO analysis shows alarming rates of overweight children ... According to a new report published by the WHO Regional Office for Europe, being overweight is so common that it risks becoming a new norm in the WHO European Region. For example, up to 27% of 13-year-olds and 33% of 11-year olds are overweight. ... Some countries have managed to contain the epidemic; France and some Scandinavian countries at least keep it at a stable level" - http://www.euro.who.int/__data/assets/pdf_file/0013/243400/N...

"Obesity rates in France are among the lowest in the OECD, but have been increasing steadily ... Obesity rates are relatively low among children too, and have not been growing over the past 20 years" - http://www.oecd.org/els/health-systems/obesityandtheeconomic...

Perhaps you don't know what overweight looks like because you are used to the "new norm"?

"More than a third of overweight teenagers do not regard themselves as too heavy and think they are about the right weight, a study in England shows. ... Over the last few decades, studies in adults have hinted that fewer people are able to spot when they are overweight. And scientists speculate that the rising levels of obesity across the population might have "normalised" the idea of being overweight or obese, making it harder to recognise the extra pounds." - http://www.bbc.com/news/health-33453456

> I'm 21 years old in a western European country and barely anyone my age is overweight

That explains it. Come to the USA, it is the exact opposite.

Obesity is heavily correlated with poverty.

As inequality around the world grows, so will obesity, so at median, people will get less fit, while the outliers will become more athletic.

I hate to say it, but correlation is not causation. Unless you can provide some studies that show people who get rich e.g. from lottery winnings, also lose their weight and vice versa with proper controls for depression and the like there is no reason to believe that an increase in economic inequality will lead to an increase in obesity.

The lottery winner sample is a bad one because the argument about poverty causing poor health behavior is an overall lifestyle problem and not just a resource one.

Children who grow in the upper middle class or upper class will grow up with access and encouragement to participate in physical activities, parents who are better informed and able to construct healthier eating habits and the resources and cultural permission to use mental health professionals as needed.

Winning a 100 million jackpot after growing up poor can't change that.

That's a relatively recent development though.

Obesity used to be heavily correlated with being a member of the aristocracy. Gout used to be a disease of the rich. Now everyone has the opportunity.