This is very much a loaded question, but have you ever looked into the longetivity of the Californian Mormons, who as far as I know eat animal products?
You joke, but it has been going on for a while: The Global Influence of the Seventh-Day Adventist Church on Diet (https://www.mdpi.com/2077-1444/9/9/251/htm). And obviously as mentioned by another the processed food industry etc.
Do you happen to have any idea if your g- and grandparents on the Indian side eat and or ate a lot of refined carbs like naan or white rice? Refined carbs being often called a modern thing and the cause of metabolic disease, but so far I've not really found that to be true.
I guess you are talking about life expectancy being way lower back in the day. Those numbers are massively skewed by infant mortality and so many other things (infections, complications during child birth, ...) that are nowadays easily sorted out by antibiotics and other means.
A lot of people actually do follow them. If you check https://fns-prod.azureedge.net/sites/default/files/nutrient_... (from https://www.fns.usda.gov/nutrient-content-us-food-supply-190...) you can see saturated fat consumption going down as recommended, chicken consumption going up, even things like sugar has gone down recently. These obviously vary between country, but here in Finland people at large do seem to follow the guidelines especially considering school and work canteens, retirement homes and so on.
It isn't even just the trans fats in vegetable oils it is the amount of polyunsaturated fats (omega 3 & 6) which are present in amounts that are basically impossible to find in the wild and don't react well when heated up.
"During the last three decades, 4-hydroxy-2-nonenal (HNE), a major α,β-unsaturated aldehyde product of n-6 fatty acid oxidation, has been shown to be involved in a great number of pathologies such as metabolic diseases, neurodegenerative diseases and cancers."
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3824598/
"Overall, beef fats produce less HNE and total secondary lipid oxidation products under thermal treatment, compared to pork and chicken fats as well as most vegetable oils."
Source: https://conservancy.umn.edu/handle/11299/191191
Single stomach animals such as humans, pigs and chicken store whatever fat they consume somewhat in the same form whereas ruminants like cows do not, hence the fact that pork and chicken fats oxidise easier as they are nowadays fed a not very ancestral diet.
Some omega 6 amounts in oils (sourced from Fineli https://fineli.fi/fineli/en/index):
- Sunflower seed oil n-6 polyunsaturated fats 62.3g
- Canola oil n-6 PUFA 22.1g
- Olive oil n-6 PUFA 10.4g
That Wikipedia article doesn't seem to cite very many studies. At least from my own perspective I can tell you that even after two hours of eating many kinds of meals your blood sugar can rise and you will need insulin to counteract that, either produced by the body itself or injected.
As an aside I would really like to know where the two hour postbrandial measuring for blood glucose levels etc. comes from as it feels completely arbitrary.
T1D here who has a CGM, this is not true for me at all. Without _enough_ insulin on board spaghetti would start spiking my blood sugar ~20 minutes after consumption and the sky is the limit. With something like steak I could basically skip injecting insulin beforehand, but would need to inject later to deal with the delayed rise. The rise from protein in general is never anywhere near as drastic as from carbs, even the "healthy" carbs.