Red meat generally from beef and pork used to be more lean, but
since the mid 1900's those who raised such animals for slaughter
fed them corn and now antibiotics to make them fatter. Of course
the extra fat give them a better flavor. But eating a lot of fat is bad
for humans. Not so much if you work hard or live in a cold climate.
Which most of us don't. And when I say work hard, I mean burning
five thousand calories or more a day.
It wasn't unusual for people to eat 10 pounds of food a day when they
were working hard in pioneer days. They worked hard and died young.
Probably so young that cancer didn't have a chance to kill very many.
When I do eat meat it's usually turkey or chicken. Not so much red meat.
I had bowel surgery two years ago, and at that time no sign of cancer.
Ah, always a sensible voice to these discussions!
I like to point out that even when unprocessed, the meats from our livestock little resemble what our ancestors were used to consuming, which would have been relatively lean in most circumstances. Furthermore, meat would have been a merely supplementary source of food in many ethnic groups, with heavier consumption in the winter when less vegetation was available. I've got a pet theory that increased meat consumption along with reduced light exposure during the wintertime trigger a pseudo-hibernating metabolic state that encourages fat retention, but as far as I know nothing of the sort has been proven yet. Guess that makes me a crank, then. Nevertheless, if you want to accept that theory: Don't treat meat like a staple food in combination with a sedentary lifestyle.
Grass-fed, organic beef is closer to what our physiology is adapted to. And of course, poultry is much leaner, most of the time. Fish is quickly becoming a radioactive, heavy metal -laden luxury due to pollution and unsustainable practices, but everything I've read suggest fish itself has a very healthy nutritional profile.
And it's delicious. 
