I would contest that. If you dig more into it, you'll find the obesity crisis started around the late 70s with a change in dietary guidelines and medical guidelines saying basically 'fat & meat bad' and 'carbs good' along with the widespread introduction of vegetable oils, leading to too much insulin and other hormonal effects slowly increasing diabetes & obesity in our population.

Read "The Obesity Code" if you want a more detailed description with a lot of links to papers and studies for more info.