Between 1971 and 2000, obesity doubled. Look at what happened to macronutrients at the same time (above).
People ate way more carbs and much less saturated fat. Maybe that was not such a great idea?
Of course this is only statistical correlations, but if you want even more check this out:
There we have it again. More carbs, less of everything else, and somehow people end up eating more and gaining weight (data from this study on US men).
Do you think it’s all a big coincidence?