I get your point but olive oil is nowhere near as prevalent as sugar. Some products even market themselves as "premium" for containing olive oil.

sesame oil, corn oil, sunflower oil, coconut oil, and palm oil have the same caloric density as olive oil, are roughly as digestible, and have been cheap and cultivated by humans for far longer than the obesity pandemic. i'd mention suet and lard, too, but it turns out that those have somewhat lower digestibility, so i don't want to confuse the discussion

by contrast, sugary foods commonly have about the same caloric density as healthy foods

so i think caloric density is clearly an important factor (you won't get fat by pigging out on lettuce and tomatoes unless you add salad dressing) but the comment i was rebutting gave the following simple, clear, and wrong explanation of the obesity pandemic

> I think the primary cause of the obesity epidemic is the widespread availability of cheap calorie dense food and a few hundred million years of evolution devoted to making biological machines designed to consume as much calorie dense food as they could find

and that just isn't an accurate description of the situation