I'm in agreement with low fat diet but ... it needs moderation of other habits along with it.
As for use of butter. In moderation I see no current research proving it is a problem. I refuse to use margarine as it is deadly, IMHO. Hydrogenated and/or partially hydrogenated fats are the killer. Research shows margarine to be linked with problems with artherosclerosis. Our bodies don't know what to do with it..so, sadly, it gets stored in arteries, etc.
An adult has no neded for milk as you can get calcium from dark green vegetables and other dietary sources quite easily. Adult drinking of milk is a dietary mistake. Milk causes excessive creation of mucus and that invites colds and other respiratory problems.
Of course, this doesn't even mention the practice of the dairy industry's massive usage of hormones and their feeding dairy cows tons of antbiotics. I'm just not interested in drinking antibiotcs or hormones, thanks.
Give me Butter or Smart Balance any day.
Re grandparents lifestyle
Here's the deal as I see it. Our grandparents had a significantly different lifestyle. They worked longer and harder physcially. They did a hell of a lot more walking and daily 'labor'. They also didn't have the 'advantage' of TV in their midst. So their bodies were built in a way that is tougher and that toughness protected them.
Unscientifically, I've noticed that in modern cultures where people watch less TV and have a more physical routine (while having a modern medical system with diseases under control) they live healthier longer, too. Parts of Japan (in the mountainous region) have the greatest concentration of 90+ yr olds in the world. My guess is that it's partially their genes - but it also could be their lifestyle (less cars, pollution and more walking and physical labor).