Metabolic flexibility is called the ability of our body to handle the different immediate principles (fats, glucose and proteins) through the different metabolic pathways in a harmonic way, maximizing energy efficiency.
Mainly, the body handles glucose and fats, but in certain situations and conditions of need it also makes use of organic proteins, production of ketone bodies and the glutamine pathway, among others, in order to maintain metabolic functions.
What is metabolic flexibility?
Metabolic flexibility is the ability of our system to respond to the metabolic needs of the body. This concept derives from the inferences obtained from patients affected by obesity, metabolic syndrome and type 2 diabetes.
When referring to metabolic flexibility, from the most common conception, it is in the context of the management of fuel sources between the fasting and postprandial phase, together with the management and efficacy of insulin.
Insulin acquires a predominant role around metabolic flexibility due to insulin resistance offered by tissues due to environmental (obesity) and genetic (type 1 diabetes) conditions; this concept was first proposed in 1931 by False and Boller.
This insulin resistance is key to what is known as metabolic inflexibility, which can develop in different tissues, especially muscle tissue, liver and fat tissue.
An example of metabolic flexibility can be found in different independent studies, where endurance-trained athletes are able to handle fatty acids after lipid overload, without the need to use their glycogen stores within the muscle, thereby reducing oxidation of glucose.
Symptoms of metabolic inflexibility
Do you need to eat before training? Do you get dizzy if you go for a run without having eaten before?
These are questions that we can ask ourselves or that often occur in poorly trained or untrained people during the development of sports activities. In specific cases it may be the result of metabolic alterations secondary to genetic alterations, but they are the least.
These questions bring us closer to the sensations that occur in people with metabolic inflexibility due to poor use of metabolic resources and routes, both for anabolic and catabolic purposes, mainly due to poor fat management.
This metabolic inflexibility may be conditioned, in part, by mitochondrial alterations. These are organelles responsible for energy metabolism and can be affected by dietary imbalances, especially when there is a fat weight gain and physical inactivity.
All of the above are signs that the ability to properly use fat (mainly) as an energy source has been lost.
It is important to recover this capacity and know how to use glucose in some environments and fat in others.
What signs and symptoms may appear when there is an alteration or decrease in metabolic flexibility?
- One of the most prominent clinical signs of metabolic inflexibility is insulin resistance.
- Hyperinsulinemia, secondary to insulin resistance.
- Hyperglycemia, in advanced stages the body is not able to overcome insulin resistance producing hyperglycemia.
- All this gives rise to the metabolic syndrome, which sometimes evolves into type 2 diabetes mellitus.
- The symptoms that we find can range from difficulty to exercise in appropriate conditions, to states of hypoglycemia after exercise.
- Dizziness, sudden loss of strength and early exhaustion during sports.
- All this leads to an increase in systemic oxidative stress, which ends up affecting, if it is maintained over time, liver, kidney, cardiovascular function…
How to achieve metabolic flexibility?
To achieve adequate metabolic flexibility, we must abide by the evolutionary and adaptation principles of our organism. This pushes us to return to the ancestral diets, and more common, in our case the Mediterranean diet, but hyperproteic diets, intermittent fasting, caloric restriction, etc. are also useful.
At present, the radical changes that have occurred in the last century thanks to technological advances have led us to produce and consume products to which we are not naturally exposed. So our body must adapt to the new dietary conditions in which there is an excess of food intake, together with a reduction in daily physical activity.
This is why to achieve greater metabolic flexibility we must:
- Exercise regularly.
- Balanced diet, be it intermittent fasting, caloric restriction, etc.
- Eliminate highly processed and refined products.
- Management of chronic physical and emotional stress levels.
Intermittent fasting and metabolic flexibility
Caloric restriction improves insulin sensitivity, even in the absence of weight loss.
Both fasting and caloric restriction without fasting have been shown to be useful for weight loss, with this weight loss, together with the introduction of physical exercise, being the two main keys to recovering metabolic flexibility or improving it if it is not affected.
Intermittent fasting in all its variants has independently shown weight loss , health benefits, demonstrated by the reduction of fasting insulinemia and, therefore, reduces metabolic inflexibility in patients with above-average insulinemia levels.
Metabolic flexibility and immune system. How to achieve immune-metabolic flexibility?
Inflammation may also be related to metabolic flexibility, as inflammation can be reduced in adult patients with good metabolic flexibility.
As an example we have the elderly. This segment of the population shows higher levels of sustained low-grade systemic inflammation and metabolic inflexibility; demonstrated by the increase in inflammatory mediators, these involved in multiple processes such as arthritis, type 2 diabetes mellitus, neurodegeneration, cancer, etc.
This inflammation leads to the infiltration of inflammatory cells in the tissues and organs, potentially damaging them, aggravating the initial situation, giving rise to or favoring the appearance of metabolic inflexibility, by altering the metabolism of fats. We must bear in mind that fatty tissue is an endocrine organ that is highly involved in low-grade chronic inflammation.
Among the inflammatory mediators involved, the most prominent are: IL-6, IL-1, TNF-a and CRP, in addition to the total leukocyte count. On the other hand, we have anti-inflammatory mediators that seem to have a protective role, such as IL-10.
So how to achieve immunometabolic flexibility? Through physical exercise and a balanced diet, the inflammatory profile of patients can be changed, thus reducing or at least slowing down the development of chronic pathologies and favoring the use of energy resources as a result of an increase in metabolic flexibility.
Benefits of improving metabolic flexibility
Once we make the decision to change our eating routines and implement measures that normalize our metabolism (for example: performing physical exercise) we will find multiple benefits by recovering our metabolic flexibility. Between them we have:
- Improves physical and cognitive performance.
- Greater energy efficiency.
- Reduction of fatigue, thanks to the better handling of the immediate principles.
- Reduction of the probability of developing cardiovascular diseases.
- Weight maintenance at healthy levels, reducing the appearance of metabolic syndrome and type 2 DM.
- Improved quality of life and life expectancy.
- Improvement of digestive function and energy resources and their routes.