High-carbohydrate vs. low-carbohydrate diets

Humans, as omnivores, differ from other animals in terms of diet with one undeniable advantage: Their metabolism shows considerable flexibility in utilizing energy sources, which allows them to adapt to great extremes.

This feature, called “metabolic flexibility” nowadays, is increasingly being consciously used by those interested in rational nutrition, without realizing what exactly they are manipulating and what the consequences of such “playing” with the hidden potential of their own body are. Most experimenters come from two areas – weight reduction and sports.

Every tool available in life, like a coin, has two sides. It can thus be a good servant, but also a bad master. Since it is an approach to diet connected with energy production, the explanation and understanding of this whole issue needs to be perceived primarily from this perspective.

In simplified terms, we can claim that we consume food for:

1. Energy sources, which ensure the functioning of every cell,
2. Nutrients, which serve as building blocks of cells,
3. Flavors, which give rise to emotions that control our behavior.

In the area of energy sources, evolution has bestowed us with several options. As the main driving force of life, we are able to obtain energy from:

- Carbohydrates (sugars),
- Fats (fatty acids),
- Proteins (amino acids).

The chemical processes leading from the breakdown of basic macronutrients to the use of their metabolites as an energy source are well known. We know that the main source of energy is carbohydrates. Mainly because they are readily available, quickly and easily metabolizable, and in our conditions (historically perceived since the emergence of agriculture), simply the most advantageous for metabolism. The fact is that with a mixed (= high-carbohydrate) diet, the body uses sugars to a much greater extent than another component, which is fats (fatty acids).

From the perspective of energy metabolism, there is a fundamental difference between sugars and fats, which lies in the speed of their utilization. Carbohydrates are generally considered “fast” fuel, while fats are a “slow” source of energy. The body also has the ability to use some amino acids as an energy source, although not nearly to the extent as with the previous two macronutrients.

An intriguing feature of energy metabolism is the ability to “switch” under specific conditions into a mode where the main source of usable energy is ketone bodies, which are products of fat metabolism. These situations occur in cases of starvation or for various reasons when we remove the main sources of carbohydrates (grains, legumes, fruits, certain types of vegetables, sweeteners) from our diet. Once the body loses sources of “fast” energy, it is forced to use ketones (breakdown products of fatty acids) as an alternative.

These ketone bodies are therefore an alternative source of energy.

From this perspective, it's clear that in simplified form, based on knowledge about the composition of diet, we can define two ways of eating:

1. High-carbohydrate,
2. Low-carbohydrate.

Each of them has its advantages and disadvantages, so it is wise to view and evaluate both in a holistic manner. Only such an approach will lead us to understanding the sensibility of choosing any of them.

Basic Characteristics of High-Carbohydrate Diets

• Allow consumption of carbohydrate sources
  This type of menu thus displays the most important characteristic of diet - variety, which ensures the body a very wide range of substances having a direct impact on human health. The high-carbohydrate system therefore allows eating representatives of all food groups, due to the representation of carbohydrates the category of plants is obviously important – grains, legumes, vegetables, fruits, nuts, and seeds.

  Besides being the basic source of carbohydrates in simple and complex forms, these foods provide essential vitamins, minerals, antioxidants, a range of phytonutrients, fiber… And since diet variety is one of the most important rules of eating, it's essential to perceive the freedom of food choice as a significant asset. In this regard, the high-carbohydrate approach provides much more benefits than its counterpart in the form of low-carbohydrate regimes.

• Contain a higher proportion of carbohydrates
  A relationship is presented in the form of:
  - The amount of grams of nutrient per kilogram of body weight – in high-carbohydrate diets, the amount is commonly presented as around 3-5 grams of carbohydrates per 1 kilogram of total body weight.
  - The percentage share of total energy intake – in the high-carbohydrate concept, it is 45-60%.

• More accommodating to taste
  The taste of food that we perceive during its consumption leaves very strong traces in our emotional sphere, which arise from birth. Tastes give rise to emotions, emotions lead to the production of endorphins (hormones of “good mood”). The taste of a dish is determined not only by its preparation but also by the content of individual components. The most influential taste is sweet; therefore, a high-carbohydrate diet is more diverse in taste, and we develop a much stronger relationship to it than to low-carbohydrate diets.

• Burden the pancreas
  To use carbohydrates as an energy source, the pancreas must produce enough of the hormone insulin to allow sugar to enter cells. The more carbohydrates we eat, or the more often we consume them, the more insulin the pancreas must supply. This carries risks of overburdening the pancreas and simultaneously developing insulin resistance and subsequently even type 2 diabetes.

• Are evolutionarily younger
  The human genetic code was exposed during evolutionary development to the diet of hunters and gatherers for the most extended period. This diet was based primarily on consuming meat/insects, nuts, seeds, berries, and available sources of vegetables and fruits. Its composition was typically low-carbohydrate because it contained minimal grain, legumes, and fruit, which are the richest sources of carbohydrates. The turning point occurred approximately 12,000 years ago when agriculture started to emerge, and the share of carbohydrates as an energy source in the diet began to overtake fats. With this, the adaptation of metabolism to the higher load on the pancreas and all consequences arising from this new way of eating also increased. The high-carbohydrate system is thus evolutionarily younger, building upon the low-carbohydrate one.

Moreover, it has persisted long enough for our genome to adapt to these conditions. However, this does not mean it is “better” or conversely “worse.” From a factual perspective, it is younger, and our bodies can function well with it. But, overconsumption of carbohydrates brings several negative impacts on our health, so it's necessary to regulate their quantity.

Basic Characteristics of Low-Carbohydrate Diets

To properly evaluate the characteristics of low-carbohydrate regimes, it's first necessary to agree on their definition and possible categorization. Low-carbohydrate diets (commonly called low carb) contain a much lower proportion of carbohydrates than high-carbohydrate ones. Because carbohydrates are a fast energy source and their content affects the functioning quality of every cell in the body, two subcategories of diets are distinguished:

Low Carb Diets

The first is generally called “low carb.” The recommended amount of carbohydrates per day is generally around 120 grams, although this figure is quite approximate. It is based on the presumed need to ensure enough energy sources for the human brain, for which glucose is the only energy source in high-carbohydrate eating. With lower carbohydrate intake, mental fatigue increases. Basic characteristics of “low carb” diets:

• Contain lower carbohydrate content
  In choosing the range of foods, we are forced to limit or eliminate representatives of grains, legumes, and often even fruits. Thus, the diet does not exhibit variety, theoretically risking a lack of some micronutrients.

• “Spares” the pancreas
  Reducing carbohydrate intake results in less insulin release. This way of eating significantly reduces the risk of those civilization diseases caused by carbohydrate excess. This includes insulin resistance, type 2 diabetes, and certain inflammatory diseases.

• “Forces” higher animal food consumption
  In most cases, with the absence of legumes, grains, and fruits, animal foods begin to prevail. This increases the ratio of animal proteins over plant ones, which means a higher burden on the liver, which is forced to process protein metabolism products.

Ketogenic Diets

The second type of diet is called “ketogenic.” It relies on the metabolism's ability to “switch” to using alternative energy sources in the form of ketones. Ketones are products of fatty acid breakdown that occur under specific conditions, either through starvation or by reducing carbohydrate intake below a certain threshold (most commonly 50 – 40 grams throughout the day) while simultaneously increasing fat intake.
Characteristics of ketogenic diets:

• Contain almost no carbohydrate sources
  The average daily carbohydrate intake with these diets ranges between 30 – 50 grams. The diet thus becomes strongly stereotypical in its choices of foods. The same applies to the taste experience that food provides. Except for a smaller portion of vegetables, nuts, and seeds, all plant food sources need to be avoided. The diet may be deficient in various micronutrients (vitamins, minerals, phytochemicals, antioxidants), which in practice often means the necessity to secure their alternate sources, i.e., supplements. This increases both the financial and organizational demands of implementing such a diet.

• “Encourages” higher animal food intake
  The diet is based on an excessively high share of animal sources of proteins and fats. A high share of meat and fat sources (cheeses, butter, oils…) mainly burdens the liver and gallbladder, and this should always be considered.

• Are evolutionarily older
  Because this is the original, evolutionarily older way of eating, it must be understood that we are very well adapted to this type of diet. In trying to transition from a high-carbohydrate system to this, however, it is necessary to invest enough time for the body's systems to adjust. A healthy person “switches” to the ketogenic mode after diet adjustments, generally within three days. One of the main conditions for inducing ketosis is the proper activity of the intestinal microbiota. If this is not in order (and often it is not due to excessive use of antibiotics, too much stress, and poor nutrition), the metabolism will simply not allow an individual to enter this way of energy functioning.

• Ensure stable energy distribution
  Compared to glucose, ketones have one crucial advantage - they do not cause fluctuations in blood sugar levels. In ketosis, the energy source for cells is consistent. During a ketogenic diet, we avoid energy swings, fatigue, and hunger, which are presented, alongside fat reserve reduction, as one of the greatest strengths of this way of eating.

• Are not suitable for everyone
  A ketogenic diet also has several contraindications. Due to health risks, individuals with heart diseases and vascular problems (angina pectoris, myocardial infarction, stroke), cancer patients, type 1 diabetics, pregnant and breastfeeding women, children, and possibly people with psychological disorders should avoid it.

• Are more challenging to implement
  Because these diets require careful attention to what exactly is eaten, the effort to eliminate carbohydrate sources and significantly increase fat intake is a certain challenge in everyday life.

Ketogenic and low carb diets have become a trend over the last few years. It’s not really surprising since, as a society, we have moved towards an extremely high representation of carbohydrates in food, leading to the emergence of many civilization diseases. Many thus see resolving this situation in adopting the exact opposite way of eating, starting to favor low-carbohydrate diets.

However, this isn’t a victory since every eating method has its pros and cons, and risks on both sides need consideration. An interesting “compromise” approach includes systems like intermittent fasting, whose principle is based on dividing the day into two phases - fasting and feeding. During the time when we do not eat (this includes the period of sleep and the subsequent several-hour period), the body processes excessive carbohydrate reserves and directs metabolic processes towards the ketogenic regime.

The feeding phase – if well conceived and not turned into an opportunity for excessive eating – is most commonly based on a mixed diet, i.e., high-carbohydrate eating, and kickstarts metabolism in the desired direction. Essentially, this regime simulates a state to which we adapted very well during the relatively long period of hunters and gatherers, and this adaptation is still present in our genes today.