Fat is not all that much different, but one thing that's happened is the type of fat has changed a lot, and so people are eating less fat from plant sources and more fat from animals sources That's where the saturated fat comes in and high saturated fat intake is not a good thing.

脂肪摄入量相差无几,然而脂肪的种类却发生了很大变化,人们越来越少从植物中摄取脂肪,而更多是从肉类食物中获得,肉类食物中含有饱和脂肪酸,而过多地摄入饱和脂肪酸是有害的

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选