I've read most of The China Study and it is pretty interesting. The studies do show that eating animal products are causing us health problems like heart disease, diabetes and cancer (which are almost "western" diseases) and by that I mean many of us are seriously becoming part of the rising statistics. In other parts of the world, people have less chronic health problems. In cultures/regions that have healthier people, they usually have a lot more exercise (farming and transportation by foot) and they are also exposed to less chemicals. I've also read most of "Healthy at 100." Which covers the China study too, but the book mainly talks about places in the world where the oldest people live in. But they aren't just old, they don't even have heart problems, vision problems, loss of hearing or dementia.
Anyway, here is my own opinion on the different types of diets that are becoming popular.
Paleo - I don't know the specifics about this diet but I do know that whatever in the grocery store isn't actually paleo. We can no longer eat that way because... Well, bugs are gross. By that I mean our ancestors used to eat everything. We couldn't just buy stuff, we had to eat what we could find. For example, if you eat broccoli, cabbage, Brussels sprouts and cauliflower in a day, they're all different vegetables. However they are all cruciferous vegetables. Nothing wrong with that, but that isn't what paleo is about. Maybe I'm not well informed, but I think the (real) paleo diet should include many many different types of food, which we cannot find at the grocery store.
Atkins/low carb diet - while it makes sense that our bodies aren't designed for processing lots of sugar, our brain prefers glucose as its primary source of fuel (correct me if I'm wrong). Our muscles and liver store glucose in the form of glycogen. We have these abilities for a reason. The low carb diet is supposed to work by lowering the amount of insulin, and because insulin makes us store fat. (I don't remember exactly how)
But the problem with the low carb diet is that it is low in calories. No fruit or grains. Only meat and veggies basically. When your body is low in calories it will digest your own muscle. Long story short, it is not sustainable and you will likely lose muscle along with the fat. It works for losing weight, but it isn't exactly a healthy way to do it.
Here is my opinion on the whole food, plant based diet.
People on this diet are guaranteed to be healthier than someone on the vegan diet. What's the differences? Well, vegans may be very strict with animal products, but not with processed foods. Chips are vegan, for example, but not healthy. If you are eating whole foods, you get more nutrients in your body.
I believe that evolution-wise, we should be eating meat. (We have those canine teeth or whatever they're called) HOWEVER the meat we get from the factory farms these days are full of chemicals and toxins. Therefore we are probably better off not eating it. So I'd say that it isn't "meat" that is the problem, but it is the meat we get from the store that is harmful to our bodies.
Milk - Probably not even good for us. But one thing for sure, it's unnatural and our bodies aren't designed to digest it beyond a certain age (I think after we are toddlers or babies). Also, it comes from a cow. It's weirder to drink off a cow than from mommy... Which no longer supplies us with milk, duh.
Animal fat vs plant fat - both fats have their own problems. But lately I've been reading that plant oils like corn oils and vegetable oils are very high in omega 6 which is inflammatory. Olive oil and coconut oil continue to be healthy fats. But in all honesty I think saturated fats from animals are more natural than corn/veg oil because it's attached to the meat we eat whereas some oils are chemically extracted.
Whenever I eat stuff I just think about if it exists in nature. Is it normal to eat it?