Look towards your grandfather's daily activities and not just his diet. My grandparents too lived to a ripe old age eating foods that make so called experts cringe. The real difference between them and our generation was that they never led a sedentary lifestyle.
Sometimes I believe the office style of work that many celebrate; because it freed them from the fields and such; probably is the least beneficial change we have made.
Look towards your grandfather's daily activities
and not just his diet
Oh, definitely.
The point I tried making is that we cannot pinpoint yet the exact cause for the trends in heart-disease, obesity and diabetes. You simply cannot blame it all on meat, or on eggs, or on carbohydrates.
In fact it's quite the opposite ... by making changes to the diet of our grandfathers, we risk a ton of negative side-effects. People nowadays drink low-fat milk, but our grandfathers were drinking whole milk straight from their own cows without problems. And our metabolism is a complex mechanism - we forget that homo sapiens were unable to digest milk, but now we digest it just fine, so it's definitely a mater of context, like culture and genetics.
And personally I tend to blame this all on three things - sedentary lifestyles, stress and preprocessed crap that contains sugar, with sugar being the only common compound that is partly carbohydrate, partly lipid, while also being a nutrient that our grandfathers had little access to.
Chronic stress and sleep deprivation are known to have horrible effects on personal health -- up to, and including, fat storage and cardiovascular fitness. The extent of these effects has not received enough attention, and may be greater than we currently realize. I strongly suspect that, in the next ten or so years, we'll see a surge of scientific studies documenting the importance of these factors on health.
Over the last few decades, much fuss has been made over the societal switch from whole foods to processed foods. But people have been getting less and less healthy every decade, obesity rates have been increasing each decade, and food hasn't grown all that substantially more processed in the last few decades. (People in the 70s and 80s ate nearly as much processed junk as we do, and they were healthier on average. People in, say, Japan eat a metric fuckton of foods processed beyond our recognition, and they're healthier than we are).
Processed foods are probably to blame for our obesity crisis in some respect, but they're not the single issue. We should be taking a closer look at lifestyle factors, especially sleep and stress. Americans don't sleep enough, and lead more stressful work lives, than the citizens of almost any other developed country on the planet. (It's actually debatable if we're more or less sedentary than other nations, too. Pretty much everyone in white-collar work is sedentary these days, by the clinical definition of the term, and working out even an hour a day is not going to completely mitigate the effects of sitting on one's ass for the following 10 hours).
People in the 70s and 80s ate nearly as much
processed junk as we do
I suspect you're from the US. Your statement is simply not true, at least not for Central/Eastern Europe.
For instance in Romania we had no McDonalds until the early 1990s and they were amongst the first to enter, before other junk food providers like KFC, Burger King and such. One friend from the US visiting me was surprised that we only have 2 or 3 Starbucks joints in our capital that has a population of more than 2 million people.
And regarding preprocessed junk, the trend is very recent here. People used to laugh at such things as low-fat milk, or frozen French-fries / Pizza.
The result: I've never seen so many obese people in my life as I've seen in the US, but we're catching up.
Sorry, I should have clarified that my implied frame of reference was the US. But you're right. There seems to be a pretty linear correlation between obesity rates and the "American way of life," however we want to quantify its variables: processed foods, sleep deprivation, etc. Generally speaking, the pursuit of convenience at the cost of all other considerations.
And I don't deny that processed foods are major factors in the obesity problem, and probably necessary factors. But I'm saying that they don't seem entirely sufficient to account for the increased obesity rates within the US, which has been gorging itself on processed junk for 30+ years now.
probably is the least beneficial change we have made
Maybe, but there are trade-offs. For example, would you rather live to 100 but bust your ass every day, or live to 90 doing a desk job? Many people would pick the latter.
Sometimes I believe the office style of work that many celebrate; because it freed them from the fields and such; probably is the least beneficial change we have made.
We are not designed to be idle.