A tremendous amount of research points to a plant based diet being the best diet to prevent most of our top 10 diseases of affluence killers.
Animal protein consumption over 10% of our daily calories has been shown to contribute to the promotion of cancer, heart and artery disease, diabetes, dementia, MS and many other diseases. Yes, 10%, that is not a type-o. We have been so brainwashed into thinking that protein is what is keeping us thin and alive and that carbs are evil. White bread, candy, doughnuts etc. are not good carbs and not whole foods, but they are what have given carbs the bad rap that they now have. Thanks to the Atkins Keto, and Paleo camps for furthering the fear of eating anything but protein and all the fat that usually goes along to it! Nicely done. I can find 100 diet books on the shelf at the library and you could probably lose weight following any of them BUT they will not be cancer/heart disease/stroke/diabetes/autoimmune disease proofing you, and most of them are not long term solutions to maintaining weight loss. Of course this is probably the reason that 90% of people gain the weight back after following a fad diet.
Check out these links for good articles(explore the links in the ones that have links) about diet and how it relates to preventing disease:
Heart Disease
Cancer
Diabetes
Stroke
Dementia
Auto-immune Disease
If we eat the standard American diet (SAD), we do not eat enough nutrients due to our high consumption of meat and processed foods. Once we cut these out we are nourished by consuming a good variety of plant based foods. We get high amounts of micro and macro nutrients including lots of inflammation fighters from whole plant based foods. Eating this way gives us everything our body needs (with the exception of vitamin B12 which is a supplement vegans should take). A lot of people will argue that a meatless, dairyless diet will not give us enough protein, fill us up, or keep us strong. They are WRONG. Research supports this and I have to say that I have never felt stronger or better since I went veggie.
It is tough to be obese on a whole food plant based because what you are eating is not super caloric. Because it is so nutrient dense, it is very filling. Most of these foods are also not addictive (as calorie dense meat, sugar, and processed foods are) so people generally do not overeat them.