There needs to be a lot more studies on obesity and why it's gone up so much. I don't buy the "more sedentary lifestyle" argument. Our mobility hasn't changed THAT much in the last 50 years, at least not enough to explain the absolutely skyrocketing cases of obesity.

There's a big link between poverty and obesity. People in poverty tend to be more active due to more physically demanding jobs, so it feels like the cause has to be from cheap food. While a lot of people might immediately look to high fructose corn syrup, I'm not sure it's that simple. Obesity rates are rising even in places that don't use HFCS in everything. I wouldn't be surprised if there was some additive or preservative that started to get heavily used in the last few decades that's had horrible, unintended consequences.