> you need to substitute a plant food that is also relatively calorie dense (like beans, lentils, or potatoes)
I tried this; not much help. I was used to a diet of essentially no carbs (and had found it beneficial for me), and actually switched because I had a friend who would not shut up about not eating meat and wouldn't stop until I did. I can indeed eat more, but occasionally I would get full and still not feel "full".
> meat is harmful to our circulatory health
I'm not so sure about this one. I've read about the adverse effects of IGF-1 with respect to cancer, but that seems to be more because it is a growth hormone. Is it any wonder a growth hormone can cause caner to grow? IGF-1, by keeping new cells forming, could help mitigate things like lower bone density and lower muscle tone with age.
I've tried replacing protein-calories with carb-calories. I gained a good amount of weight doing so, and didn't feel nearly as good. I'm much happier and healthier back on my old diet. Lots of meat (mostly white)/eggs/fish, a good amount of veggies, some fruit, lots of nuts, lots of dairy. Almost no sugar/soda/fried stuff/other such junk.
Maybe different people do best on different diets, and we should recognize that what's good for one is not always good for another. What irritates me is when people get sanctimonious about it and say that I'm evil if I don't eat their diet, even when my quality of life, health, and productivity is significantly better doing it my way.