I mentioned posting about this a while ago but never got around to it so... here it is!
I have done extensive research on the subject of how our bodies process macro-nutrients and in this post I hope to explain:
A brief history of human evolution as it pertains to our diets
How our bodies process macro nutrients
How high fat diets work
How high carb diets work
How heart disease works (and why saturated fat both is and ISN'T the cause)
And other considerations related to high fat and high carb diets
One of the challenges of researching a topic like this is that people on both sides of the issue are very passionate that they are "right" but few people take ALL of the data into consideration. But... What if we're both right? Regardless of which side of this debate you fall on, please consider ALL of the information presented before forming an opinion or dismissing any of the data points presented that don't support your existing belief system. It all ties together.
They are just data points.
A Brief History of Human Evolution
Humans have evolved over the course of millions of years (approximately 3.5) and during that time our bodies have been very finely tuned to thrive in a multitude of environments and conditions which include: tropical jungles, the arctic, islands, the great plains, deserts and the GREATEST landscape of all, the wooded forests of the Pacific Northwest . Starting from our evolutionary roots, we know that we have a close association with primates. Primates eat a plant-base diet that consists largely of fruits, leaves, nuts, seeds, stems and small amounts of insects and other bugs. These evolutionary origins can clearly be seen in yourself by simply opening your mouth and looking in the mirror and not so easily observed in ourselves by the length of our digestive tracts. Herbivores and omnivores require longer digestive tracts because it takes longer to break down the fibrous plant material that we eat and extract as many of the nutrients as possible. Carnivorous animals have comparatively shorter digestive tracts as protein and fat are much easier for the body to process and store.
As primitive humans began to evolve into more dexterous and intelligent creatures, we began to spread out and needed to adapt to different climates and new ways of nourishing our bodies besides those methods employed by our early chimp relatives. Scientific research shows evidence of the mastery of fire (used for cooking) around 100,000-200,000 years ago. Finally, we could start eating meat! In general, foods that we've evolved to eat taste good in their unprocessed state. Thus, you wont see anyone gnawing on a raw rib-eye outside of a few unsavory bets... Unlike carnivorous animals, our bodies aren't well suited for consuming raw meat. We don't have the flesh-shredding features they do and our bodies can't protect us from the foodborne pathogens present in raw animal tissue. Cooking GREATLY reduced the amount of chewing required to consume plants and meats (allowing us to consume the great quantities of them needed to power our growing brains) and also protected us from foodborne illnesses. To facilitate this new lifestyle option, our bodies improved its ability to consume the large amounts of saturated fat and cholesterol associated with eating a diet based on animal products.
How our bodies process macro nutrients
Our Bodies Run on Sugar. When you look at sports drinks and other post-workout supplements you'll find HEAPS of sugar. Our muscles burn sugar, which is fed to them by a process called Glycogenesis. This replenishes our muscles, allowing us to maintain peak performance levels longer and recover from exercise more quickly. If this doesn't happen, your performance suffers and thus, Gatorade and its associated multi-billion dollar industry was born. Sugar also stimulates the release of insulin and IGF-1, which is arguably the MOST anabolic (aka muscle building) hormone our bodies produce. One fitness celebrity (a dumb one, Jim Stoppani...) even went so far as to recommend eating Pixy Sticks and Gummy Bears as a post-workout snack because, it doesn't matter how you get the sugar, you just need sugar. Some professional cyclists will even mix as much as 200 grams of refined sugar with water for a syrupy sweet drink to keep their blood sugar levels topped off while performing their intense multi-hour exertions. There is also an emphasis in the fitness community around meal timing; eating directly after a workout so that your spiked blood sugar levels refill your muscles glycogen stores and maximize that nice insulin spike to make the most out of your workout. Evolutionarily, this also makes sense as we hunt and then feast. Gather and gorge. If sugar and carbohydrates are not present though, like our ancestors who ate animal-based diets, our bodies have adapted to meet our needs and avoid Hypoglycemia (low blood sugar) by turning non-carbohygrates (protein and fat) into sugar through a process called Gluconeogenesis.
Another critical component of our body is our brain, which also runs on sugar. Like our muscles, our brain also suffers when it doesn't have access to an abundant supply of sugar in our blood. As Dr. Kelly McGonigal, a Stanford psychologist and author of The Willpower Instinct (amazing book) and Charles Duhigg, author of The Power of Habit talk about in their books, our brains have evolved over millions of years in a fairly crude manner. As new portions and functionality were developed, they were just kind of slapped on top of the older, more primitive parts that were still needed to perform basic unconscious and semi-conscious tasks. Back in the true paleolithic era, nutrition and energy was very scarce and our bodies adapted to be as efficient as possible (there are many other things our bodies do to conserve energy that I won't go into here). That being said, our brains consume a ton of energy to operate at full power, so our bodies developed a way to throttle back the activity in some of the newer, and more energetically expensive portions, most notably, the Prefrontal Cortex. Our PFC is responsible for many of the things that make humans "human". Decision making, planning, deciding between right and wrong and willpower. Many studies have been done around the effect that blood sugar has on your ability to resist temptations and follow instructions. Upon further investigation, studies have shown that as soon as our blood sugar levels begin to drop, the brain doesn't just scale down PFC activity linearly to match the dropping blood sugar levels, it dramatically scales back activity as soon as it detects a drop in blood sugar (blood sugar and self-control: http://psr.sagepub.com/content/11/4/303.abstract).
Q: But there is substantial evidence sugar and carbs are making Americans fat and sick!
A: This is true. Refined sugar and refined carbohydrates do bad things to our bodies. Refined sugar, in the quantities that we consume it in (as discussed in the documentary Fed Up and the book Salt Sugar Fat) from modern chemically-engineered "food products", spike our blood sugar enormously high which doesn't give our body a chance to use the sugar (as described above) like it normally would, triggering a huge insulin response that also results in a blood sugar valley, leaving the consumer fat and lethargic. Allow me to reference, the stereotype that everyone has of obese people. Refined carbohydrates (such as white flour and white rice) are also processed by the body much more quickly than their unprocessed counterparts and have a similar effect.
So why are fruit, brown rice and whole grains supposedly "health" foods if they all turn to sugar eventually and our body can't tell the difference between the sugar in fruit and high-fructose corn syrup? The packaging. Fruit has something that the other processed foods don't have: Fiber. Fiber slows down the digestive process and as a result, the sugar is extracted from the fruit slowly while it traverses our longer digestive tract so that you get a slow even stream of sugar to your blood preventing the spikes and crashes that begin the "fat and lazy" cycle associated with refined sugar. The same is true for whole grains and unprocessed (brown) rice; the additional fiber slows digestion and feeds your brain and muscles a nice slow and steady stream of glucose to keep them running at optimal performance. This slower rate of absorption helps prevent unused sugar from being stored as fat.
High Fat and High Carb
As discussed in the documentary Forks Over Knives, there is evidence in our stomachs that supports two lifestyles; the mechanisms that triggers satiety (aka, feeling "full"). Our stomachs signal the brain using one of two ways: it detects the richness of our food via fat content or, it detects how physically full the stomach is by measuring how much it has stretched. Again, you can see how these mechanisms play into our two diets. If you're eating rich fatty animal tissue, you don't need as much food to meet your bodies caloric needs. With a plant-based diet, which is less calorie-dense (and doesn't contain much fat), you need to eat until you're physically full to get enough calories.
To support these theories we have TONS of observational evidence. There have been hundreds of studies that show, the more plants you eat, the healthier you are. I mean just talk to any vegan and they'll chat your ear off about all of the amazing health benefits they've experienced since they cut meat, dairy and animal products out of their diets. But... now we have this new group of people joining the conversation claiming the opposite: "I cut fruit and carbs out of my diet and ate mostly animal products and now I'M experiencing all kinds of health benefits and weight loss" (sources here here and here). There have also been studies of indigenous tribes who eat diets that consist of 70% of their daily caloric intake from the saturated fat of wild plains-graising animal sources (milk, blood, organs, marrow, brains, ect...) who live normal, healthy lives. So... what the heck is going on?
How heart disease works (and why saturated fat both is and ISN'T the cause)
For decades, research has directly correlated saturated fat consumption with Atherosclerosis and increased risk of heart attacks and strokes. Studies have even been done where they take a control group of vegetarians, add 8oz of daily meat consumption to their diet and immediately their risk factors for atherosclerosis go up. When they remove the meat from their diets, their risk factors go down. So, saturated fat and cholesterol from animals is the problem! But, that still doesn't explain why all of these people, who eat diets which contain as much as 70%! of their daily caloric intake from saturated fat (most of which is from animals), aren't falling over dead left and right.
To explain my answer to this contradiction, let's take a quick look at a few foods that are more recent additions to our diet and we all seem to generally recognize as being "unhealthy" and see what they have in common...
Pizza
Cheese Burgers
French Fries
Ice Cream and Milkshakes
Cakes and Cupcakes
Potato Chips
All of these foods are high in carbs AND high in fat. So, knowing that humans can thrive on diets that are high in carbs OR high in fat, how can we explain this interaction? I would also like to highlight and interesting phenomenon related to these new high-fat diets: when you first start following a high fat diet, people often report symptoms associated with hypoglycemia during their "transition period". They go through a period of extreme low blood sugar as their body begins to ramp up its Gluconeogenesis. Cardiac surgeons around the world also KNOW that the atherosclerotic build up that is responsible for heart disease is made up of fat (among other things). To me, the answer is very obvious and there is only one conclusion that can be made which explains ALL of the data available:
While our bodies blood sugar needs are being met through carbohydrates (and/aka sugar), it is not able to remove saturated fat from the blood quickly enough to prevent the build-up of fatty plaques in our arteries, resulting in atherosclerosis which leads to heart disease, heart attacks and strokes.
There has not been sufficient scientific research done to back up this conclusion and this is my personal opinion based on the research I have done. I have not seen this theory tested anywhere or even discussed (or if it has been discussed, I haven't seen it). Again, this is 100% based on my own opinion but there is no other way to explain the evidence both for and against saturated fat as it relates to heart disease.
The Diets and Other Considerations
High Carb: While following a plant-based whole foods vegan diet you'll focus on consuming the following foods:
Legumes (beans, peas, lentils, ect..)
Oats
Brown Rice
Starchy Vegetables (Corn, parsnips, potatoes, pumpkin, squash, zucchini, yams ect..)
Non-Starchy Vegetables (Lettuce, asparagus, broccoli, cauliflower, cucumber, spinach, mushrooms, onions, peppers, tomatoes ect..)
Fruit
it is very easy to lose weight as plant-based food is naturally very calorie dilute. 1 pound of sweet potatoes is only 400 calories and costs about 99 cents! And you can bet that will fill you up! This can cause problems however, as we're socially conditioned to eat sparingly which can result in malnutrition. As discussed earlier, for low fat diets, satiation is triggered by the stomach being physically full. When following these natural diets, It is always best to listen to your body. It is also important to eat a variety of greens and other plants, not just focusing on one - even if it's kale! (just like with any diet)
Because cholesterol is only found in animal products and there are very few plant-based foods that contain large amounts of saturated fat, a plant-based whole-foods vegan diet is the only diet that have been proven to prevent and reverse heart disease.
High Fat: These diets were popularized for their weight loss potential (initially marketed as Low Carb) as American's have a notoriously difficult time giving up fatty meat which doesn't pair well with the sea of carbs found in modern processed foods. Refined carbohydrates are added to many food items, even some you wouldn't expect. If you plan to follow a high fat diet it is VERY important that you eliminate ALL carbohydrates possible. The underlying principal is that your bodies only energy source is fat. This allows you to maintain the, fat friendly, gluconeogenetic state. Despite that the diet is called "high fat" you should still be consuming a large volume of vegetables to aid in digestion. Failing to do so, might be the cause of some cancers (referenced below).
Following a High Fat diet, you'll want to focus your caloric intake on the following:
Non-Starchy Low-Sugar Vegetables (Lettuce, asparagus, broccoli, cauliflower, cucumber, spinach, mushrooms, onions, peppers ect..)
High-Fat Meats and Fish
Eggs
Plant-based oils high in fat such as Olive and Coconut Oil
Full-Fat Dairy products such as: Milk, Cheese, Butter an Creams
I want to make two points REALLY clear - if you are following a high fat diet, you need to consume AS FEW CARBS AS POSSIBLE and LOTS OF VEGETABLES. We are not carnivores. If you do not do both of these things, you set yourself up for long-term health problems. When you are first transitioning to a high-fat diet, it is advisable to do so with a short fast (~24 hours). This will give your body a chance to burn off any remaining blood sugar and kick-start gluconeogenesis.
Various cancers have been associated with red, processed and cured meats. The World Health Organization even went as far as to group processed and cured meats in the same carcinogen category as cigarettes and asbestos! (http://www.who.int/features/qa/cancer-red-meat/en/) One explanation for this could be that most consumers of animal products don't get an adequate supply of dietary insoluble fiber which results in greatly increased risks for colon and other cancers as the meat fermenting in their digestive tract poisons their body.
High-Fat diets have existed for hundreds of thousands of years, but we don't have good data that shows the long-term health consequences of following a diet of this style in the current environment we live in. We eat factory farmed meat and dairy products (even if its organic), we live 20-40 years longer than our ancestors and we have an enormous amount of environmental pollutants which are up to 100 X more concentrated in animals than they are in the original plants themselves. If you're substantially overweight though, nothing is more unhealthy than excess body fat and an animal based diet might be easier to follow.
My final thoughts
Another important consideration for the applications of these diets is... CONTEXT! The plainsmen and women of the tribes in the high-fat examples, as well as our ancient relatives, were consuming animals and animal products that were free range, "organic", pasture raised and living off of food sources which didn't contain any environmental pollutants. Animals serve as a concentration point for environmental pollutants (which are stored in fat). Modern farming practices also feed animals diets which are not natural to their evolution in the interest of increased growth rates along with being given hormones and antibiotics. Beef cows grow at a rate of about 3 pounds PER DAY! That is not natural. Before justifying this by saying "well I eat grass fed beef!" every time you eat at a restaurant, you are eating factory farmed meat. The claims made by the animal agriculture industry related to the conditions in which the animals are being raised are largely done to make consumers feel better about purchasing their products. For many of the marketing terms used, there is either no legal definition or loose guidelines around what it constitutes to make those claims (which are not enforced by any government agencies) with the exception of Certified Organic products. For example, "grass fed" cows for the production of beef can, and are, still given hormones and antibiotics to increase their survivability and growth rates (another example of misleading advertising here).
As described in the documentary Cowspiracy, animal agriculture is also wildly unsustainable and animals cannot be raised in an efficient enough way to meet the growing demands that our population has. As a result, animal agriculture has tried to keep up by bending the rules and side-stepping ethics which has lead to this unfortunate set of statistics...
#1 cause for species extinction
#1 source of greenhouse gas emissions (51% of all greenhouse gasses world wide)
#1 cause for Ocean Dead Zones
#1 cause for water pollution
#1 cause of rainforest deforestation
it consumes 55% of all the water used in the US (2,500 gallons of water per 1 pound of beef produced)
livestock or livestock feed cover 1/3 of the Earth's ice-free land
The US government pays out $38 billion each year to the meat, dairy and egg industries in incentivized funding. Unfortunately, these funds go almost exclusively to massive factory farming corporations. Fishing isn't much better as 200 million pounds of Bycatch are pulled from our oceans and killed EACH DAY. Animal agriculture is also notorious for brutal torturings, mutilations and the systematic abuse of animals. Private organizations began to infiltrate these large operations and expose the abuse with hidden camera footage that proved the abuse was on-going and not isolated incidents which resulted in felony convictions and firings! Fear of bad press and losing government funding from these exposures, these corporations bought politicians to pass laws that made it illegal to expose animal abuse, known as Ag-gag laws. Laws such as AETA have also been passed to aid these businesses in using the legal system to attack those that would expose the evils that they are perpetrating. If that isn't absolutely disgusting and evil then I just don't know what is.
While we are biologically capable of eating both plant-based (carb) and animal-based (fat) diets, I hope you'll consider the impact of your decisions to consume animal products. Eventually, it wont be a choice. Animal product production simply cannot keep up with the growing needs of our species and the only reason it has kept up thus far has been from unethical agricultural practices that have taken an enormous toll on the environment. It is not impossible to raise and slaughter animals ethically, but it is not profitable, scaleable or sustainable enough to meet the current demands.
@Simon Zackrisson @ZenMonkey @Draconis Chaser
