We're also a lot more sedentary. I am convinced without being able to produce proof, that this is the biggest problem - the lack of physical work.
I used to believe we eat shit, but my ancestors were really poor and basically ate just a few food types most of their life. I think I've come a long way and am convinced that, even if I were to eat a very occasional McDonalds, it'd still be eating a lot better. It's a lot more diverse and that really makes a difference. Don't know about you but I very rarely eat the same thing two days in a row.
Nutritionally I see what you mean and definitely agree, people are taller than they used to be and until recently have lived longer. But all of the benefits a nutritionally diverse and rich diet brings are easily undone (and more) by also consuming enough sugar to become obese. This is why the current generation of obese kids at school have a lower life expectancy than their parents despite better healthcare and nutrition in their early years.
This is why I think that jumping on the "BPA must be the problem!" answer to low count question is a bit ridiculous, especially when people are becoming more unhealthy by the day. People who eat more processed sugary foods and drinks that come in BPA containing packaging are also more likely to be obese and unhealthy too.
Lacking physical work also does not account for all of the weight gain we are seeing at the moment - obesity rates remained stable in the '60s and '70s when we lived similarly lazy lives. (1)
Food industries have influenced what people think of as 'healthy' so much, even as it's shifted over the years, that people believe they're eating healthier when really they're not.
Protein bars, granola, multigrain, fruit juice, don't have high fructose corn syrup, just have a bunch of sugar instead, it's more natural!, etc and having sugar and wheat and soy and other crap put into almost everything you buy at a supermarket has contributed to this mess.
My general rule of thumb is if you're not having at least 3-4 solid servings of vegetables (not fruits, just veggies), every day, excluding corn (corn should be stripped of its vegetable status), you're probably not eating anywhere near as healthy as you should be. Fruits don't need to be avoided, but you shouldn't think you're eating healthy if you're eating 5+ servings of them every day, since they do have sugar in them (offset a bit by the dietary fiber, but still sugar).
I used to believe we eat shit, but my ancestors were really poor and basically ate just a few food types most of their life. I think I've come a long way and am convinced that, even if I were to eat a very occasional McDonalds, it'd still be eating a lot better. It's a lot more diverse and that really makes a difference. Don't know about you but I very rarely eat the same thing two days in a row.