for best health I need much more animal fat than I usually get — is plausible:
1. As Spector said, butchers cut the fat off meat. The odds that our Stone-Age ancestors, living when food was sometimes scarce, did the same thing: Zero. Perhaps our meat is unnaturally low in fat. If for a long time in our evolutionary past we ate a lot of animal fat it makes sense that our bodies would be shaped to work best with that much fat.
2. Many video games, which boys enjoy, resemble hunting. I think this reflects an evolutionary past in which men hunted. If so, for a long time humans ate meat. That they ate a lot of meat is suggested by the fact that when big game went extinct (probably due to hunting) human health got worse.
3. American culture demonizes animal fat. The conclusion that animal fat is bad rests on epidemiology. Once something becomes heavily recommended or discouraged, a big problem for epidemiologists arises: the people who follow the advice are likely to be different (e.g., more disciplined, better off) than those that don’t (the healthy-user bias). As I blogged yesterday, an example is vaccine effectiveness: Those who get vaccinated are different than those who don’t.
4. Fat tastes good. Which implies we need it. We like whipped cream, butter on toast, milk in tea, and so on. Butter vastly improves toast even with my nose clipped. Long ago, when this fat-pleasure connection evolved, dietary fat was mostly animal fat and fish oil.