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.
I work in a manufacturing company that was owned by the founder for 50 years until about 4 years ago when he retired. He disagreed with a lot of the ideas behind lean manufacturing so we had like 5 years worth of inventory sitting in our warehouse.
When the new management came in, there was a lot of squawking about inefficiency, how wasteful it was to keep so much raw material on the shelf, and how we absolutely needed to sell it off or get rid of it.
Then a funny little thing happened in 2020.
Suddenly, we were the only company in our industry still churning out product. Other companies were calling us, desperate to buy our products or even just our raw material. We saw MASSIVE growth the next two years and came out of the pandemic better than ever. And it was mostly thanks to the old owners view that "Just In Time" manufacturing was BS.