Metabolism is a complex physiological process made up of a series of chemical reactions that take place in living organisms, with the purpose of obtaining the energy necessary to sustain life. In simple terms, metabolism ensures the burning of calories to produce the energy required for the optimal functioning of the body’s physiological processes.
Metabolism: Definition, Types of Metabolism, and Roles
Metabolism consists of two physiological stages that occur sequentially: catabolism and anabolism.
Catabolism refers to the breakdown of food-derived macronutrients such as carbohydrates, proteins, and fats. For example, digestive enzymes break down ingested carbohydrates to obtain glucose, which enters the bloodstream and can be used immediately for energy or stored in the liver and muscles as glycogen.
Anabolism is the opposite of catabolism and refers to the body’s ability to assemble small units, such as amino acids, to form large molecular weight proteins. Anabolism is an essential mechanism for growth, development, healing, and tissue regeneration.
Factors That Influence Metabolism
The main factors that play an important role in modulating metabolism include age, sex, body composition, level of physical activity, and hormonal function.
Aging is physiologically associated with a slowing of metabolism due to muscle mass loss and changes in body composition.
Men generally have a faster metabolism than women because they typically possess greater muscle mass.
Estrogen and testosterone influence fat distribution and muscle mass, having a direct effect on metabolism. Muscle tissue has a higher metabolic activity compared to adipose tissue.
Maintaining a high level of physical activity speeds up metabolism by increasing the body’s energy requirements during exercise.
Types of Metabolism
The metabolism of living organisms can be classified as follows:
Primary metabolism, involved in basic chemical transformations essential for maintaining vital processes, growth, and development. This includes the metabolism of carbohydrates, fats, amino acids, and nucleic acids.
Secondary metabolism, which ensures the execution of certain individual chemical processes in the body through hormones, antibodies, pigments, or structural molecules that make up the rest of the body.
Basal Metabolism
Basal metabolism represents the totality of mechanisms involved in providing the energy necessary to maintain the function of vital organs such as the heart, lungs, kidneys, nervous system, digestive system, and liver.
Basal Metabolic Rate
The rate at which metabolism converts ingested food into usable energy is called the metabolic rate. The minimum amount of energy required by the body for survival is known as the basal metabolic rate (BMR).
How Is Metabolic Rate Calculated?
Metabolic rate is calculated based on sex and age and is expressed as the number of calories burned per hour to provide the energy necessary for body function.
However, according to current research, the accurate calculation of metabolic rate must also include height and weight and is determined using the following formulas:
Men:
66.4730 + 13.7516 × weight (kg) + 5.0033 × height (cm) − 6.7550 × age (years)Women:
655.0955 + 9.5634 × weight (kg) + 1.8496 × height (cm) − 4.6756 × age (years)
Metabolic Rate and Weight Control
A low metabolic rate predisposes individuals to faster accumulation of excess body weight, both at rest and during physical activity. In contrast, a high metabolic rate indicates the body’s ability to rapidly break down and use nutrients for energy without storing them as fat.
This explains why people with a slow metabolism gain weight more easily even with a moderate caloric intake, while those with a fast metabolism can maintain an ideal weight even when caloric intake exceeds daily expenditure.
Why Metabolism Slows Down – Causes
The main factors that can frequently lead to a slowdown in metabolism include:
Nutritional vitamin D deficiency, which can cause disturbances in glucose metabolism
Restrictive diets or, conversely, excessive caloric intake, which can disrupt metabolism
Deficiency of certain enzymes, such as in phenylketonuria, which prevents the breakdown of specific proteins
Hormonal imbalances such as hypothyroidism
Use of certain medications (e.g., corticosteroids) or toxins (chronic alcohol consumption)
Are There Foods That Speed Up Metabolism?
Certain chemical compounds found in chili peppers, green tea, and coffee can increase metabolic rate. According to studies conducted so far, green tea consumption can increase daily metabolic burn by up to 260 calories when combined with regular physical exercise. Capsaicin found in chili peppers can increase metabolic rate when taken as concentrated dietary supplements.
Ginger powder can intensify metabolic burning, although its effect on body weight has proven insignificant in individuals aiming to lose weight. Cayenne pepper is an extremely effective spice for boosting metabolism and can be used in a wide variety of dishes. Cocoa powder stimulates metabolic burn and can be consumed with milk or replaced with dark chocolate.
High-protein foods temporarily increase metabolic rate. The recommended protein intake ranges between 0.8–1 g of protein per kg of body weight. Chicken, turkey, fish, lentils, beans, and avocado are key protein-rich foods that can accelerate metabolism when consumed at each main meal. Daily egg consumption can aid weight loss due to its high protein content, but it is important to adjust the quantity according to individual needs.
Fast Metabolism – Benefits
Increasing metabolism through diet and physical exercise is an excellent method for weight loss even during rest, without physical effort. Other benefits of a faster metabolism include improved immune system function and energy levels, better mood and blood circulation, and enhanced detoxification mechanisms in the body.
Fat Metabolism
Lipid metabolism refers to the body’s ability to synthesize, break down, and use dietary fats with the help of specific enzymes. These complex chemical reactions are indispensable for maintaining energy homeostasis, forming cell membranes, and synthesizing hormones.
Lipid metabolism involves several compounds, including lipolytic enzymes such as pancreatic lipase, bile acids that aid in fat emulsification and absorption in the intestine, and lipoproteins responsible for transporting fats through the bloodstream.
Each tissue has a specific role in lipid metabolism. The liver is the primary site of lipid synthesis and metabolism, producing cholesterol and lipoproteins. Adipose tissue mainly stores triglycerides and releases them when the body’s energy needs increase. Muscle tissue can metabolize fatty acids to generate energy during sustained intense physical activity, while the brain can use ketone bodies derived from lipids during periods of food restriction.
