Metabolic Flexibility - An Overview

Introduction

Metabolism refers to the ability of the compounds to break down and provide benefits to the body for normal functioning. Here, metabolic flexibility means the body’s metabolic rate (the rate at which the food is digested and the fats present are converted into energy) to adapt and react to metabolic needs. This concept can give a picture of insulin resistance and the body's alteration of fat and glucose mechanisms, eventually leading to obesity or type 2 diabetes. On a broader concept, this condition explains the situation causing insulin resistance and its correlation with type 2 diabetes mellitus.

The concept of metabolic flexibility was initially studied to learn about the helmentics of parasitic worms and their ability to adapt to changes. However, metabolic flexibility has been studied from insulin stimulation and resistance. Metabolic flexibility also shows a specific response to the condition after food or overnight fasting.

The study of this concept of metabolic flexibility also refers to the fact that there is an increased amount of metabolic activity in both fasting and while performing physical exercise. Fat, adipose, and skeletal muscles are the two main tissues that function predominantly in metabolic flexibility. However, the energy expenditure varies depending on the condition, whether for a shorter or longer period.

What Are the Factors Compromising the Metabolic Flexibility of the Body?

By conducting clinical studies on many patients with obesity and diabetes, a list of factors was understood that, in turn, affected the metabolic flexibility of the body.

• Insulin Resistance from Fasting to Feeding in Obese and Diabetic Patients: This talks about how the skeletal muscles accelerate the fuel's energy. According to the measurement scale of glucose and fatty acids based on the respiratory quotient, a healthy transition of fuel shifting occurs from fasting to feeding. This occurs mostly due to increased glucose metabolism and its oxidation in the skeletal muscles. However, this transition in insulin release after a meal occurs as a major shift, leading to metabolic diseases of the heart, metabolic syndromes associated with diabetes, insulin resistance, etc.

• Fluctuation of Fuel in White Fat Cells: In comparing skeletal muscle and white adipose tissue, there has been limited research on the metabolic flexibility of white adipose tissue (WAT). WAT was initially thought of as a reservoir of lipids; however, WAT has recently become known for its vital function in the metabolism of glucose and lipids and additionally for its ability to support the process of thermogenesis. Through a finely regulated free fatty acid absorption, ester conversion, and release mechanism, white adipose cells buffer circulating free fatty acids (FFAs) for peripheral tissues such as skeletal muscle and liver. This method requires the presence of glycerol kinase, which was previously thought to be absent in adipocytes. In the healthy scenario, the principle of coordinated metabolic flexibility among tissues demands that the more fat is retained in WAT post-meal, the less fat is available for catabolism by other tissues, resulting in a greater reliance on carbohydrate oxidation.

• Metabolism of Fatty Acids and Insulin Resistance: Insulin resistance is considered a primary component of improving the flexibility of metabolic activity. The body comprises sixty to eighty percent of its glucose response to that of insulin; it also requires several muscular activities to compensate for insulin resistance in the skeletal muscles of patients with type 2 diabetes mellitus. A reduction in the amount of glucose penetration in the fat and muscle cells causes a decreased production of glucose, compromising the activity of the pancreas. Although it is difficult to precisely state that the cause of insulin resistance is from the muscles or fats or because of the liver and its enzymes, it is a well-addressed scenario that insulin often precedes increased blood sugar levels.

• The Amount of Energy Needed to Support Form Resting to Working Out: Intramuscular glycogen, triglycerides, plasma glucose, and plasma fatty acids all work together to fuel active muscle. Performing physical exercises can drastically increase energy expenditure and the demand for it. This is described based on how the fat burns during physiological and biochemical exercises, where during moderate to severe activity, skeletal muscle contributes to more than 95 percent of energy requirements. Many human trials have been conducted on young, normal-weight participants with significant metabolic flexibility in fuel selection.

What Are the Health Conditions Associated With Metabolic Flexibility?

Although metabolic flexibility is considered a physiological or more chemical process, underlying medical conditions may lead to decreased metabolic flexibility. Some of the conditions associated with metabolic inflexibility are:

• Suppression of glucose oxidation due to increased fat.

• Alteration in the phenotype of metabolic genes.

• Oxidation of fat.

• Diabetes - A clinical condition characterized by an increase in blood sugar levels

How Does Exercise Help with Metabolic Flexibility?

Physical activity can increase rates of fatty acid oxidation both at rest and during acute activity. Exercise improves insulin sensitivity while lowering the risk of diabetes and cardiovascular disease. Increased insulin sensitivity with exercise training increases muscle glycogen stores, which improves endurance exercise performance. Several different pathways lead to higher insulin sensitivity and metabolic flexibility with exercise training. If spending energy is what it takes to reduce insulin resistance and improve metabolic flexibility, the movement of the body through exercise is the best option that can be provided.

Conclusion

Metabolic activity has been well studied over the past few years, where the energy expenditure from fasting to food intake while resting and exercising has consistently been a changing factor. This change in the body's metabolic functioning can directly or indirectly influence the systemic functioning of the internal organs. Hence, it is necessary to keep the body's metabolic activity in momentum to achieve better health, prevent the slowdown of metabolic functions, eliminate toxins, fatigue, feelings of fullness, bloating, restlessness, etc. and have an active mind. Also, a considerable amount of metabolic flexibility can be improved by having a thorough knowledge of the basal metabolic rate and its functions and increasing the susceptibility of this metabolic rate to increase the possible chances of energy expenditure.