> We know this because we have hunter-gatherer populations who consume 50% of their diets in sugar (e.g. the Hadza) or fats (e.g. Intuit), and they have none of the diseases of abundance found in modern populations because they have near zero obesity.
The often-cited studies suggesting Inuit populations were protected from heart disease (Bang and Dyerberg, Feldman et al) comes from limited data which has since been refuted as unreliable and insufficient. The hypotheses they generated don't hold up to the greater balance of data we have, and despite attempts to confirm findings, it simply hasn't happened.
Some studies have suggested to a lesser degree that Inuit populations have marginally smaller rates of coronary artery disease (and other cardiovascular complications), but far more have determined that rates are the same or in some cases/time frames even worse, and risk of stroke has generally trended higher as well. These are all incidents of mortality which have a very, very high correlation with diets which are high in animal fats (as well as salt, regarding strokes).
I agree that obesity is a major issue (especially in the case of sugar; it appears less harmful to the body when the sugar is needed and thus used immediately, but harmful when it hangs around and gets turned into fat. This is the main cause of the surge in fatty liver disease, for example), but there is very little and often very poor evidence that obesity is what causes atherosclerosis to occur and become a mortal danger. It seems to be dangerous regardless of weight, and exercise doesn't appear to be wholly protective against it either.
Inuits have actually served as a good example as to why this is true. Even when their obesity rates were lower, their lifestyles required more activity than average, and when studies accounted for BMI, their CAD rates were still on par with western populations according to most data.
The often-cited studies suggesting Inuit populations were protected from heart disease (Bang and Dyerberg, Feldman et al) comes from limited data which has since been refuted as unreliable and insufficient. The hypotheses they generated don't hold up to the greater balance of data we have, and despite attempts to confirm findings, it simply hasn't happened.
Some studies have suggested to a lesser degree that Inuit populations have marginally smaller rates of coronary artery disease (and other cardiovascular complications), but far more have determined that rates are the same or in some cases/time frames even worse, and risk of stroke has generally trended higher as well. These are all incidents of mortality which have a very, very high correlation with diets which are high in animal fats (as well as salt, regarding strokes).
Here is one very good look at this type of data, and if you look you can also find others: https://pubmed.ncbi.nlm.nih.gov/25064579/
I agree that obesity is a major issue (especially in the case of sugar; it appears less harmful to the body when the sugar is needed and thus used immediately, but harmful when it hangs around and gets turned into fat. This is the main cause of the surge in fatty liver disease, for example), but there is very little and often very poor evidence that obesity is what causes atherosclerosis to occur and become a mortal danger. It seems to be dangerous regardless of weight, and exercise doesn't appear to be wholly protective against it either.
Inuits have actually served as a good example as to why this is true. Even when their obesity rates were lower, their lifestyles required more activity than average, and when studies accounted for BMI, their CAD rates were still on par with western populations according to most data.