The human body is designed to consume complex and simple sugars (carbohydrates) as its primary fuel. This is absolutely scientifically indisputable. Our taste buds are designed to primarily seek out sugars and salts. We have no taste buds designed to taste specifically for meat, unlike your cat. Since we have no meat specific taste buds, most of the flavor of meat comes from the potentially carcinogenic flavor compounds that are created from the Maillard reaction, which takes place when meat is cooked. Most humans find the taste of raw unseasoned flesh to be unappetizing.
Our digestive tract contains relatively huge amounts of amylase, an enzyme that’s designed to breakdown starchy sugars. Amylase is the most abundant enzyme in human saliva. The length of our digestive tract is identical to a chimps, as is the structure of our teeth. Our digestive tract is 12 times the length of our torso, compared to a 3 times length for carnivores. Humans have convoluted complex colon walls designed to extract maximum nutrients from fibrous plant matter, unlike carnivores that have smooth straight colons. Our metabolic system is optimized to burn carbohydrates directly rather than create them from protein, unlike a carnivore.
We have no teeth designed to tear flesh from hide or impale animals. Humans have no talons or claws designed to rip or slice flesh from bone. Our jaws move side to side which allows for the chewing and grinding of fibrous plant matter, unlike carnivores who can only move their jaws up and down. Carnivores do not grind their food, they rip and gulp.
Meat and dairy have no fiber, so consuming them causes humans to have constipated stools. The consumption of meat and dairy is the number one cause of constipation in humans. Our long intestinal length causes meat to rot in the bowel, leading to a 3x higher incidence of colon cancer among meat eaters.
Most carnivores can digest microbes that would kill a human, such as botulism, which is why humans are forced to cook meat before consuming it. In fact, consuming animal fat causes the body to be flooded with bacterial toxins that cause inflammation, leading to insulin and leptin resistance.
All known carnivores pant to dissipate body heat, while plant eaters have sweat glands. It’s impossible for a carnivore to develop clogged arteries from consuming too much cholesterol, which is not true for herbivores. For most people, the sight of a bloody dead animal is naturally repulsive. I don’t know a single person that would consider popping a live mouse into their mouth. I could keep going on listing differences in physiology between carnivores and humans until I had an entire novel.
Since the human body is optimized to burn carbohydrates first, before burning fat and protein for energy, low carb high fat (LCHF) diets, such as the Paleo or Atkin’s diet, cause the body to enter a state of ketosis to obtain the energy it needs. Ketosis is a starvation response mechanism humans have that allows us to survive extended periods of famine. When humans stop consuming carbohydrates for energy, the glycogen stores in our liver get used up, forcing our bodies to consume fat. This is a starvation response mechanism = FOR EMERGENCY USE ONLY.
Studies indicate that high protein diets, which can induce long term ketosis, lead to a higher incidence of cardiovascular disease and cancer. One particular study of 43,000 Swedish women spanning 16 years found, “A one tenth decrease in carbohydrate intake or increase in protein intake or a 2 unit increase in the low carbohydrate-high protein score were all statistically significantly associated with increasing incidence of cardiovascular disease”.
Another study involving 73,000 people over 6 years found that, “Vegetarian diets are associated with lower all-cause mortality and with some reductions in cause-specific mortality.” These are not your typical 24 week bullshit 100 participant studies touted by the people pushing ketogentic diets. These are some of the most comprehensive dietary studies ever conducted in the history of modern medicine.
When the body enters a state of ketosis, hunger is dissipated. Again, hunger is dissipated because this is a starvation response mechanism. The body figures you must be living in an area that is subject to a famine since there are no carbohydrates being consumed, so it also reduces your hunger. Thus, you have the ability to think clearly about finding new sources of carbohydrates to fuel yourself while you manage to get by on proteins and fats during a period of famine.
Ketosis causes a build up of acetone in the body, which is dissipated through the breath and urine. Let me say that again. Ketosis causes a build up of nail polish remover in your blood stream, causing your breath to stink. Anyone think this is a healthy state to maintain for years on end? Your body can end up cannibalizing your bones to buffer this acid build up. Elderly people on a HFLC diet should be VERY concerned about developing osteoporosis. Not only should they be concerned about developing osteoporosis, but dementia as well. Studies have shown that risk for AD is greater in people who consume diets high in cholesterol, saturated fats, and total calories while avoiding fiber, vegetables, and fruits.
Whenever someone points to studies saying a chronic state of ketosis is not harmful, all you have to do is look at the duration of the studies to see they are severely lacking as evidence. Studies that take place over the course of 6 months to a year aren’t going to show any serious side effects because that’s the duration of time the body is supposed to be able to cope with a famine. Further, since ketosis induces weight loss, people are going to initially feel better if they were overweight to start with. Cardiovascular health will improve in the short term simply due to the weight loss, but as the Swedish study shows, those benefits don’t last over the long term.
Over the long term, it’s difficult to achieve sustained weight loss eating a diet of virtually no carbohydrates simply due to the calorie densities of the foods involved. Pure fat, such as any refined oil, contains 4000 non-nutritional calories per pound. A tablespoon of oil contains 100 calories, which is the same as an entire apple or banana. Of course, the apple or banana also comes packed with a ton of phytonutrients and fiber that will keep us healthy. Fiber is absolutely critical to maintaining a healthy intestinal bacterial flora – again, meat and dairy have no fiber and cause damage to the gut flora.
Every large civilization on the face of the Earth has fueled itself primarily on starches. We know a low fat high carbohydrate diet leads to healthy slim populations of people – without any calorie counting. A billion Asians eat a diet primarily consisting of rice and vegetables. Asians who eat this traditional diet have virtually non-existent levels of obesity or metabolic disease. The same is true of any indigenous population of people who eat a starch based whole food diet. Do you honestly think all those skinny healthy Asians would be healthier eating a big fat steak every night with their bowl of rice?
And before the paleo people start screaming about the Massai and Inuit, it’s been published that neither of those tribes consume a ketogenic diet, and that the fermentation of their food leads to higher carbohydrate consumption than was previously assumed.
A plant based diet contains enough protein to power even the most athletic among us. The finest endurance athletes in the world eat a purely plant based diet and engage in carb loading before races. At most, humans need 10% of their diet to be protein, which coincidentally happens to be the level of protein that is present in most plant based sources of food.
I’ve come across several websites operated by doctors who claim that low fat diets don’t work when compared to low carb diets, or that low fat diets were found in numerous large scale studies to have no impact on various diseases or rates of obesity. If you actually look at what those studies consider to be a “low fat” diet, it turns out that all of them are basing that claim on a diet which limits fat to no more than 30% of daily caloric intake, and none of them limit meat, dairy or fatty foods consumption. 30% fat intake is a mountain of fat compared to what you would get if you ate a whole food plant based diet, which typically clocks in at less than 10%. At 30% fat intake, they may as well not be on any diet at all! That’s 3 times the fat intake of a whole food diet! 30% is only 3% less than what the average US male normally consumes!
One other thing to consider is that if humans are supposed to eat meat as their primary fuel source, it would literally be impossible to feed everyone on the planet. Do you have any idea how many more resources it takes to raise meat as opposed to growing a starch? It’s about an 80 to 1 difference in resource costs. The world can live on starches, it can’t live on meat without mass starvation occurring from shortages. People can live on a diet of nothing but potatoes indefinitely. Try doing that with any other food source.
You can learn a lot more about this topic by watching this 10 hour lecture series given by a doctor.
Dr. Michael Greger explains how his grandma was cured of end stage heart disease after being sent home to die, who then went on to live another 31 years. He also discusses the cause of insulin resistance and why people remain diabetic.