24/04/2024
Recent headlines scream that we have an obesity problem and that carbs are the culprit for the problem. That leads me to ask: How did we get to blaming carbs as the enemy in the war against obesity?
First, a quick review of the history of diet and macronutrient content.
A long time ago, prehistoric humans foraged and hunted for food. Protein and fat were procured from animal meat, which was very important for encephalization, or evolutionary increase in the complexity or relative size of the brain. Most of the requirements for protein and iron were satisfied by hunting and eating land animals as well as consuming marine life that washed up on shore.
Carbohydrates in the form of plant foods served as the only sources of energy available to prehistoric hunter-gatherers, which offset the high protein content of the rest of their diet. These were only available during spring and summer.
Then, about 10,000 years ago, plant and animal agriculture began, and humans saw a permanent shift in the macronutrient content of our daily intake so that it was more consistent and stable. Initially, the nutrient characteristic changes were subtle, going from wild food to cultivated food with the Agricultural Revolution in the mid-17th century. Then, it changed even more rapidly less than 200 years ago with the Industrial Revolution, resulting in semiprocessed and ultraprocessed foods.
This change in food intake altered human physiology, with major changes in our digestive, immune, and neural physiology and an increase in chronic disease prevalence. The last 50 years has seen an increase in obesity in the United States, along with increases in chronic disease such as type 2 diabetes, which leads cardiovascular disease and certain cancers.
Back to Carbohydrates: Do We Need Them? How Much? What Kind?
The increase in the macronutrient content of the food we eat containing saturated fat and refined carbohydrates and sugars represents a major change and is arguably the smoking gun of the obesity epidemic. Unfortunately, ultraprocessed foods have become a staple of the standard American or Western diet.
Ultraprocessed foods such as cakes, cookies, crackers, sugary breakfast cereals, pizza, potato chips, soft drinks, and ice cream are eons away from our prehistoric diet of wild game, nuts, fruits, and berries, at which time, our digestive immune and nervous systems evolved. The pace at which ultraprocessed foods have entered our diet outpaces the time necessary for adaptation of our digestive systems and genes to these foods. They are indeed pathogenic in this context.
So when was the time when humans consumed an "optimal" diet? This is hard to say because during the time of brain evolution, we needed protein and iron and succumbed to infections and trauma. In the early 1900s, we continued to succumb to infection until the discovery of antibiotics. Soon thereafter, industrialization and processed foods led to weight gain and the chronic diseases of the cardiovascular system and type 2 diabetes.
Carbohydrates provide calories and fiber and some micronutrients, which are needed for energy, metabolism, and bowel and immune health. But how much do we need?
Currently in the United States, the percentage of total food energy derived from the three major macronutrients is: carbohydrates, 51.8%; fat, 32.8%; and protein, 15.4%. Current advice for a healthy diet to lower risk for cardiovascular disease is to limit fat intake to 30% of total energy, protein to 15%, and to increase complex carbohydrates to 55%-60% of total energy. But we also need to qualify this in terms of the quality of the macronutrient, particularly carbohydrates.
In addition to the quality, the macronutrient content of the diet has varied considerably from our prehistoric times when dietary protein intakes were high at 19%-35% of energy at the expense of carbohydrate (22%-40% of energy).
If our genes haven't kept up with industrialization, then why do we need so many carbohydrates to equate to 55%-60% of energy? Is it possible that we are confusing what is available with what we actually need?
We certainly have changed the landscape of the world due to agriculture, which has allowed us to procreate and feed ourselves, and certainly, industrialization has increased the availability of accessible cheap food. Protein in the form of meat, fish, and fowl are harder to get in industrialized nations as are fruits and vegetables. These macronutrients were the foods of our ancestors. It may be that a healthy diet is considered the one that is available.
For instance, the Mediterranean diet is somewhat higher in fat content, 40%-50% fat (mostly mono and unsaturated), and similar in protein content but lower in carbohydrate content than the typical Western diet. The Dietary Approaches to Stop Hypertension (DASH) diet is lower in fat at 25% total calories, is higher in carbohydrates at 55%, and is lower in protein, but this diet was generated in the United States, therefore it is more Western.
We need high-quality protein for organ and muscle function, high-quality unsaturated and monounsaturated fats for brain function and cellular functions, and high-quality complex carbohydrates for energy and gut health as well as micronutrients for many cellular functions. A ketogenic diet is not sustainable in the long-term for these reasons: chiefly the need for some carbohydrates for gut health and micronutrients.
How much carbohydrate content is needed should take into consideration energy expenditure as well as micronutrients and fiber intake. Protein and fat can contribute to energy production but not as readily as carbohydrates that can quickly restore glycogen in the muscle and liver. What's interesting is that our ancestors were able to hunt and run away from danger with the small amounts of carbohydrates from plants and berries plus the protein and fat intake from animals and fish — but the Olympics weren't a thing then!
It may be another 200,000 years before our genes catch up to ultraprocessed foods and the simple carbohydrates and sugars contained in these products. Evidence suggests that ultraprocessed foods cause inflammation in organs like the liver, adipose tissue, the heart, and even the brain. In the brain, this inflammation may be what's causing us to defend a higher body weight set point in this environment of easily obtained highly palatable ultraprocessed foods.
Let's not wait until our genes catch up and our bodies tolerate junk food without disease progression
