Good nutrition is not taking out an entire macro nutrient, let's say for example, carbohydrates, and replacing that with meat. Whether grass fed or not, it is still meat. I have written before about the importance of carbohydrates and that our daily intake should constitute about 50-60% of our daily diet. Carbohydrates are our main source of energy and include fruits, vegetables and grains. People have been eating grains for thousands of years and grains provide many vital nutrients; it is discouraging to me that so many people are currently anti-grain. Like anything, this latest trend will pass, however, soon to be replaced by something else. Now I'm certainly not against meat and it is a personal choice whether or not you choose to consume it. I do think that meat should constitute a much smaller percentage of our daily diet than carbohydrates and having a meatless meal once or twice a week is a healthy thing. A serving of meat is generally about 4 oz for women and 5 oz for men (about the size of a deck of cards). Too much meat/protein and not enough carbohydrates can lead to the body producing something called ketones. Ketones are toxic to the body, and so the kidneys begin to flush out these toxins. This will lead to water loss in the body, which is hard on the kidneys and also puts stress on the heart. Although this water loss will look like a reduction in weight you will also lose muscle mass and bone calcium.
There are some parts of the Paleolithic (Paleo) diet that I do agree with: no refined carbohydrates, no processed foods, no refined sugars, consuming grass fed beef or wild game, and eating healthy fats. Of course - these are all components of a healthy diet. However, grains (whole grains) and legumes are also integral components of a healthy diet and these are avoided when eating Paleo.
In my opinion, the "ideal diet" is one that mimics the Mediterranean way of eating. The principal aspects of this lifestyle include a proportionally high consumption of olive oil (used for salads, cooking, bread), legumes, fruits, vegetables, unrefined whole grains, moderate to high consumption of fish, moderate consumption of dairy products (mostly as yogurt and cheese), moderate to low wine consumption and low consumption of meat and meat products. This is a very clean way of eating and provides the body with healthy fats, great complex carbohydrates, and loads of vitamins, minerals and fiber.
Within this "ideal diet' there is so much room for personal choices. As well, the ideal diet will adapt and fluctuate: daily, weekly, monthly, even yearly according to our own individual needs. Each person is different, and each person's needs vary. Nutrition and diet is often portrayed as a confusing mess of "which diet do I choose this month?" when it shouldn't be. Keep nutrition simple: consume food that "remembers" where it came from, shop the perimeter of the store, don't eat foods that your great-grandmother wouldn't have recognized, avoid processed foods and avoid boxed goods with ingredients that your 8 year old can't pronounce.