"Is this really a mystery?" They address your question on the first page. Please read a few sentences of the article, or hey, even the entire article, before trying to refute it.
A brief sample, though their whole argument is more complex:
"People in the 1800s did have diets that were very different from ours. But by conventional wisdom, their diets were worse, not better. They ate more bread and almost four times more butter than we do today. They also consumed more cream, milk, and lard. Our great-grandparents (and the French) were able to maintain these weights effortlessly. They weren’t all on weird starvation diets or crazy fasting routines. And while they probably exercised more on average than we do, the minor difference in exercise isn’t enough to explain the enormous difference in weight. Many of them were farmers or laborers, of course, but plenty of people in 1900 had cushy desk jobs, and those people weren’t obese either."
It's not clear to me that what they describe as being a "worse" diet is actually worse.
If I make a roast chicken dinner, not breast but full fat chicken, chuck some butter in the mashed potatoes, salt up the broccoli/carrots etc, it's still significantly lower in calories and higher in nutrients than lots of things people eat today.
It sounds to me that their "conventional wisdom" is more like, well, veganism or something. Milk, butter, cream, great.
Lard is a bit more marginal, sure. But I'd still rather eat lard than random seed oil deep fried whatever.
Just because folks had access to tons of fats and such doesn’t mean that this is causal to gaining weight. It has to do with how good everything tasted. The ability to have food that’s just delicious has never been easier. Not just access to spices and seasoning, but access to premade ingredients that enhance taste. That also doesn’t even account for access in terms of cost. It’s never been cheaper to get calorically dense food than the modern era.
Honestly, have you looked at a 100 year old cookbook? Most of the recipes are… crude in their implementation, to put it mildly.
Let's assume this graph is correct. Why did humans 100 years ago consume fewer calories? The body is a complex system with many homeostatic mechanisms. We stop eating when we're full (generally). What has adjusted that homeostatic thermostat upward? Why did obesity increase linearly for half a century and then suddenly increase exponentially starting in 1980? Why are wild animals and laboratory animals also more obese than 100 years ago?
But people differ in their incomes. While there always were fat rich people, if food prices were the limiting factor, your average noble from the House of Lords of 1930 would be as fat as average people are today. And yet if you look at those black and white photos of important politicians, businesspeople etc., they were way less fat than an average contemporary student.
This is the Pacific War Council in the early 1940s. Do you believe that those people, decision makers whose decisions affected lives of millions, couldn't afford to eat ad libitum?
> As to why people eat more, it's probably due to higher energy density food, advertising (especially to children) and lost norms about eating (e.g. sugary stuff is not "proper food").
Animals, wild and lab, are probably affected by human food production.
> Why did obesity increase linearly for half a century and then suddenly increase exponentially starting in 1980?
I do know one thing people used to jump on that coincides with this timing, but I don't know how likely it is to be a/the culprit - high-fructose corn syrup. It's the green line on this graph: https://en.wikipedia.org/wiki/File:US_Sweetener_consumption,...
A brief sample, though their whole argument is more complex:
"People in the 1800s did have diets that were very different from ours. But by conventional wisdom, their diets were worse, not better. They ate more bread and almost four times more butter than we do today. They also consumed more cream, milk, and lard. Our great-grandparents (and the French) were able to maintain these weights effortlessly. They weren’t all on weird starvation diets or crazy fasting routines. And while they probably exercised more on average than we do, the minor difference in exercise isn’t enough to explain the enormous difference in weight. Many of them were farmers or laborers, of course, but plenty of people in 1900 had cushy desk jobs, and those people weren’t obese either."