[tim333]

The trouble with those sorts of studies is that they don't prove much - only that there's a weak correlation between thing A and thing B which is a good starting point for research but poor evidence for drawing conclusions from in itself. To follow up a scientist might say - ok lets look as people who eat basically nothing but saturated fat and people who eat basically none and see if one group drops dead quicker. This has been done, for example traditional eskimos live basically on saturated fat from the seal like stuff they eat and their health is fine. On the other hand some stuff like man made trans fats do kill you in a measurable manner - use them as your main diet and you'll drop some years earlier which is why they are being banned - eventually after many years of such evidence. The human body is pretty adaptable and can live OK on most foods that we have evolved with so switching from nuts to meat will probably not have a dramatic effect on life span as the body can deal ok with both on the whole.