I was a fan of a vegan diet. In fact, I was a strict vegan.
I gained weight! Everyday when I went to try clothes on they just got tighter! After a few months, I became very tired, I had aching legs (and I was not the only one ), I was weaker and less energetic.
And this is something Angelina Jolie felt too, as she said "I joke that a big juicy steak is my beauty secret. But seriously, I love red meat. I was a vegan for a long time, and it nearly killed me. I found I was not getting enough nutrition." 
So I did a little research on this, reading books and articles from sites supporting vegan lifestyle or supporting high fat diets. However, one of the best sites I found that it was an eye opener, was 'roarofwolverine', where he's based on his own medical condition and not on a - cherry picked - study .
However, to be honest, I was eating mostly bread, rice, pasta, legumes and sugar. Maybe the problem is when, as a vegan, you eat mostly refined and processed carbohydrates. For example, Tim Ferriss in his book 'The 4-Hour Body' suggests eating slow carbs and the next time I will try this approach.
Most vegan supporting authors recycle the same study over and over again, to support their claims, while others base their beliefs in movies like "Forks Over Knives" or "The Chine Study", which for many, are not the best sources out there [5, 6, 7].
The caption from the above image says about meat eaters vs vegans. But this is just another vegan propaganda, the real image can be found here and it's for colon cleanse. However, according to this article,  beans, grains, and vegetables rot in your colon.
Others pointing out only studies or facts that supports their claims, like Ancel Keys did with the Seven Countries Study [8, 9]. But there are some of them pointing out irrelevant studies to support their claims, either because they didn't read them or they didn't find something valid at the time they was writing their articles.
Take for example ucdintegrativemedicine, where in an article titled "Diet and Diabetes: Why Saturated Fats Are the Real Enemy" the author writes that "Insulin resistance is caused by fat"  and points to a study to support that . However, the study titled "Rapid impairment of skeletal muscle glucose transport/phosphorylation by free fatty acids in humans." says "FFAs primarily inhibit glucose transport/phosphorylation, preceding the reduction of whole-body glucose disposal by up to 120 min in humans".
The same goes with so many vegans. The irony is huge with vegans. They eat oreos and other processed trash, thinking they are doing any good to their bodies, while they are afraid of meat, because it clogs your arteries. Even 'beyond meat' is so processed , which in my opinion is even worse than rotten meat.
Beyond Burger™ Ingredients :
Water, Pea Protein Isolate, Expeller-Pressed Canola Oil, Refined Coconut Oil, Contains 2% or less of the following: Cellulose from Bamboo, Methylcellulose, Potato Starch, Natural Flavor, Maltodextrin, Yeast Extract, Salt, Sunflower Oil, Vegetable Glycerin, Dried Yeast, Gum Arabic, Citrus Extract (to protect quality), Ascorbic Acid (to maintain color), Beet Juice Extract (for color), Acetic Acid, Succinic Acid, Modified Food Starch, Annatto (for color).
Free fatty acids have been linked with obesity and insulin resistance , but is the meat the problem? In fact lean meat is very low in fat . The real problem is the fat that comes from MUFA and PUFA , as I mentioned and before, and vegans are consuming plenty of them [14, 15, 16, 17]. So, is meat the problem? [18, 19]. You can't easily answer. For instance, a plant-based diet is associated with decreased total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol, **but not with decreased triglycerides**.  So, what vegans are saying about high triglycerides and meat consumption is false.
And if you want more, read how a vegetarian diet for 30 years left a woman with spinal neuron damage.  To continue with the health paradox, 52-year-old cardiologist John Warner, president of the American Heart Association (AHA), suffered a heart attack in the middle of a health conference. 
Another example I want to give you is from a John McDougall's speech (video below). Dr McDougall suggests to eat starch, like rice, corn, potatoes, sweet potatoes, but he doesn't tell us why. What are the underlying mechanisms behind why starch keeps us healthy and lean? In this video, Dr McDougall mentions the previous civilizations and their warriors. But what did those civilizations and previous generations have not? Processed foods, GMOs, etc. Mayans and Aztecs ate corn, yes, but it was non GMO. Do you think we have the same foods previous generations had? In 1822 the average American consumed about 45g of sugar in a year, the amount found in one of today's 12-ounch sodas. 
The Asians traditionally don't eat loads of rice anyway. It tends to be small portions with some veg and protein too. Plenty of fish (almost every day) and other animals, pickles, sea vegetables, fermented and whole foods, and they avoid sweets,  compared to a typical Western diet. But claiming it's the rice that makes them healthy is wrong. It's not one food making the difference. Rice may be a better option than pizza or cake, but don't go thinking it's making you any healthier.
Type 2 diabetics have been studied so often because of the presence in their bodies of a high number of AGEs, or advanced glycation end-products. AGEs are proteins or lipids that become glycated as a result of exposure to sugars. [20, 21]
A high carbohydrate diet causing elevated blood glucose levels leads to a process called glycation . Glycation occurs is the result of the covalent bonding of a sugar molecule, such as glucose or fructose, to a protein or lipid molecule, without the controlling action of an enzyme , leading to the formation of an Advanced Glycation End-product or AGE. This can occur in the arteries, eyes, kidneys, skin, liver, nerves, and virtually anywhere in the body. Everyone has some AGEs, but high levels are a sign of accelerated aging. AGEs have been implicated in Alzheimer's Disease, cardiovascular disease, and stroke. 
The buildup of AGEs is not restricted to diabetics. Continued high blood sugar caused by eating high carbohydrate foods is enough to cause the formation of AGEs in people without diabetes. The real problem here is the uncontrolled blood sugar. . High-carb diet also is linked to early Alzheimer's and this is a connection with AGEs. 
To measure AGEs, you need a blood test called the Hemoglobin A1c. It measures AGE production over a period of 60-90 days. A lower HbA1c means that blood sugar is under control and AGE production is minimized. 
In the following video, Vegan Gains explains Rich Piana’s autopsy results. You can see that Rich Piana had 'mild' arteriosclerosis and even Vegan Gains sounds surprised. If this huge guy, in his late forties, with his lifestyle and the way of eating plus the heavy steroid use (27 years of steroid use , had 'mild' arteriosclerosis, then don't be afraid of the meat, it won't kill you.