How Does Your Metabolism Change Over Time?

Metabolism plays a vital role in our overall health and well-being. It refers to the complex set of chemical reactions that occur within our bodies to convert food into energy. However, as we age, our metabolism undergoes various changes that can impact our weight, energy levels, and overall health. Understanding how our metabolism changes over time is crucial for making informed decisions about our diet, exercise, and lifestyle choices. In this article, we will explore the key factors influencing metabolic changes throughout different stages of life and provide insights into how we can adapt to these changes to maintain a healthy metabolism.

What is Metabolism?

a graphical image of metabolism

Metabolism encompasses the essential chemical reactions that sustain life in organisms. It serves three primary purposes:

  1. Converting the energy from food into usable energy for cellular processes
  2. Transforming food into the fundamental components needed for proteins, lipids, nucleic acids, and certain carbohydrates
  3. Eliminating waste products generated during metabolic processes

These reactions, facilitated by enzymes, enable organisms to grow, reproduce, maintain their structures, and respond to their surroundings. The term “metabolism” can also encompass the entirety of chemical reactions occurring in living organisms, including processes like digestion and the movement of substances within and between cells. In this broader context, the specific set of reactions occurring within cells is referred to as intermediary (or intermediate) metabolism.

Metabolic reactions can be classified into two main types:

  1. Catabolic reactions involve the breakdown of compounds, such as the conversion of glucose into pyruvate through cellular respiration.
  2. Anabolic reactions involve the synthesis or building up of compounds like proteins, carbohydrates, lipids, and nucleic acids. Generally, catabolic processes release energy, while anabolic processes require energy.

Metabolism involves a systematic arrangement of chemical reactions known as metabolic pathways. In these pathways, one chemical compound undergoes a series of steps, facilitated by specific enzymes, to transform into another chemical compound. Enzymes play a vital role in metabolism as they enable organisms to drive energy-requiring reactions that would not occur spontaneously. They achieve this by coupling such reactions with spontaneous reactions that release energy.

Enzymes serve as catalysts, accelerating the rate of a reaction. Additionally, they allow for the regulation of metabolic reactions, enabling responses to changes in the cellular environment or signals from neighboring cells. By controlling the rate of metabolic reactions, enzymes help maintain a dynamic equilibrium within the cell.

The metabolic system of an organism plays a crucial role in distinguishing between substances that are considered nutritious or poisonous. For instance, certain prokaryotes can utilize hydrogen sulfide as a nutrient, whereas this gas is toxic to animals. This highlights the organism’s metabolic adaptation to different substances.

The basal metabolic rate (BMR) quantifies the energy expended by an organism in carrying out these chemical reactions. It represents the overall energy consumption associated with the organism’s metabolic activities. [1]

tape measure, fruits and cup on a table

What Does Your Metabolism Do?

Your metabolism remains active and continues to function even when your body is at rest. It consistently supplies energy for essential bodily processes, including:

  • Breathing
  • Digesting food
  • Circulating blood
  • Managing hormone levels
  • Growing and repairing cells
  • Regulating body temperature

Key Factors Influencing Metabolic Changes Throughout Different Stages of Life

1. Metabolism in Childhood and Adolescence

During childhood and adolescence, metabolism is typically high due to the rapid growth and development that occur during this period. The body requires energy to support the increased demands of growth, physical activity, and brain development. However, individual variations in metabolism can exist even among children of the same age. Factors such as genetics, body composition, and lifestyle habits can influence metabolic rate.

2. Metabolism in Adulthood

As we transition into adulthood, usually in our twenties, our metabolism gradually begins to slow down. This decline is primarily attributed to a decrease in lean muscle mass, which is more metabolically active than fat tissue. With age, the body tends to lose muscle and gain fat, leading to a decrease in basal metabolic rate (BMR). BMR refers to the amount of energy the body requires at rest to maintain basic physiological functions.

In addition to the loss of muscle mass, hormonal changes also play a role in metabolic changes during adulthood. For women, the decline in estrogen levels during menopause can contribute to weight gain and a decrease in BMR. Similarly, hormonal fluctuations in men can lead to a decline in testosterone levels, which may affect muscle mass and metabolism.

Moreover, lifestyle factors such as sedentary behavior, poor dietary choices, and decreased physical activity can further contribute to a slower metabolism in adulthood. It is essential to prioritize regular exercise, including both cardiovascular and strength training exercises, to preserve muscle mass, increase BMR, and maintain a healthy weight.

3. Metabolism in Older Adults

As we progress into older adulthood, typically beyond the age of 60, metabolic changes become more pronounced. The gradual decline in muscle mass and physical activity levels experienced earlier in adulthood accelerates during this stage. This age-related decline in muscle mass, known as sarcopenia, can lead to a significant reduction in BMR, making weight management more challenging. [2]

Additionally, the body’s ability to process and utilize nutrients becomes less efficient. This can affect the absorption of vitamins, minerals, and other essential nutrients, further impacting overall metabolic health. Older adults may also experience a decrease in appetite, which can further contribute to inadequate nutrient intake and potential weight loss.

Maintaining an active lifestyle and incorporating resistance exercises becomes increasingly crucial for older adults. Regular physical activity can help preserve muscle mass, enhance mobility, and improve overall metabolic function. A well-balanced diet rich in lean protein, whole grains, fruits, vegetables, and healthy fats is also vital for providing the necessary nutrients for optimal metabolism and overall health.


Metabolism undergoes significant changes over time, influenced by factors such as genetics, body composition, hormonal fluctuations, and lifestyle choices. Understanding these changes can help us make informed decisions about our dietary and exercise habits to maintain a healthy metabolism throughout our lives.

While it is natural for metabolism to slow down with age, incorporating regular exercise, particularly strength training, can help preserve muscle mass, boost metabolic rate, and support weight management. A balanced and nutrient-dense diet is equally important, providing the necessary fuel for our bodies while ensuring optimal metabolic function.

It is crucial to remember that individual variations exist, and metabolic changes occur on a spectrum. Consulting with healthcare professionals, such as registered dietitians or physicians, can provide personalized guidance tailored to specific needs and circumstances.

By prioritizing a healthy lifestyle that includes regular physical activity, a well-balanced diet, and mindful choices, we can adapt to the changes in our metabolism over time and foster overall well-being as we age.


  1. Friedrich C (1998). Physiology and genetics of sulfur-oxidizing bacteria. Adv Microb Physiol. Advances in Microbial Physiology. Vol. 39. pp. 235–89. doi:10.1016/S0065-2911(08)60018-1. ISBN 978-0-12-027739-1. PMID 9328649.