Age-related changes in metabolism 

Aging is a natural and inevitable part of life, and as time goes by, changes occur specifically in the way our bodies handle energy. Starting early in life, metabolism is extremely active to support rapid growth and development throughout childhood. It declines starting in adulthood, and we see changes to body composition and hormones. And it doesn’t stop there; as we approach older age, the body’s energy expenditure continues to decrease and can impact various aspects of our health and well-being. 

Basics of metabolism

Metabolism is like the engine that keeps the body running. It is a set of chemical reactions that occur within the body that ultimately maintain life. When we eat and drink, these chemical reactions break down the food into energy that the body uses to breathe, move, and keep itself alive.  

There are two main parts to metabolism: 

Catabolism is the breaking down of molecules. During digestion, food components such as carbohydrates, proteins, and fats are broken down into glucose, amino acids, and fatty acids. As this process of breaking down occurs, energy is released. The body then uses the energy for essential body functions such as moving, breathing, and controlling body temperature.  

Anabolism is the opposite of catabolism. It’s the process in which smaller molecules are joined together to make larger, more complex ones. This process requires energy, which is supplied by catabolism. This building up phase of metabolism supports the growth and maintenance of the body’s tissues and organs.  

Changes in metabolism across life stages

Early in life (infancy to preteen), metabolism is at its highest. This is required to support the rapid growth and development that takes place and the energy demand associated with an increased rate of physical activity.  

In adolescence, hormones begin to influence metabolism, body composition and energy utilization. This can vary from person to person depending on certain dietary factors and the amount of physical activity one participates in.  

Metabolism is relatively stable in adulthood and will later begin to decline as we enter older age (around 60 years old). This results in further changes to body composition and potentially weight change and change in weight distribution. At this time, more hormonal changes come into play for both men and women, which impact metabolism even more.  

There is newer research that has been published based on the findings of a study called the doubly labeled water method. Where we once thought metabolism started to slow much earlier, we now know that metabolism slows by about 3% each year until our 20s, then levels off, then declines again later in life.  

Factors that influence changes in metabolism

In addition to the natural aging process, there are other factors that influence changes in metabolism. Although they vary from person to person and are complex, there are some elements we have control over. 

Physical activity  

The amount of lean muscle mass compared to fat mass can alter metabolic rate as it requires more energy to maintain the structure of muscle and contract and relax it than it does to maintain fat tissue. This is why a strength training component to an exercise routine is so important.  

Diet and nutrition 

When we eat a meal, especially one high in protein, a process known as thermic effect of food occurs, which increases our metabolism. Alternatively, caloric restriction or excessive caloric intake typically slow metabolism. 

Stress and sleep  

Poorly managed stress and irregular sleep can disrupt hormone balance and increase cortisol levels negatively impacting metabolic health.  

Chronic disease states 

Medical conditions such as thyroid disease, diabetes, and polycystic ovary syndrome (PCOS) affect metabolism, as do antidepressants and antipsychotic medications. 

Dietary and lifestyle change recommendations

In a nutshell, a combination of the following can help preserve your metabolism and maintain optimal metabolic health. 

• Eat a balanced, healthy diet with adequate protein and limited processed foods 
• Regular exercise that combines aerobic activity with strength training 
• Maintain good blood sugar control by eating regularly, every 3 to 4 hours 
• Stay hydrated 
• Manage your stress levels 
• Ensure adequate, good quality sleep 

Conclusion

While age, genetics and hormonal shifts may be out of our control when it comes to changes in metabolism, there are certainly factors that are more controllable such as consuming a healthy diet, managing our stress, and participating in regular physical activity. Educating ourselves and establishing healthy lifestyle habits will help us face age-related changes in metabolism more gracefully and with a better understanding as to why changes are occurring and what to expect. 

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References: 

Metabolism. Available at  https://my.clevelandclinic.org/health/body/21893-metabolism. Accessed on 12/29/23. 

Surprising Findings about Metabolism and Age. Available at  https://www.health.harvard.edu/blog/surprising-findings-about-metabolism-and-age-202110082613. Accessed on 12/29/23. 

What is Metabolism? Available at https://www.health.com/metabolism-7709380. Accessed on 12/29/23. 

Metabolism Changes with Age, Just Not When You Might Think. Available at  https://www.pbrc.edu/news/media/2021/metabolism-milestones.aspx. Accessed on 12/29/23.

The Truth About Metabolism. Available at https://www.health.harvard.edu/staying-healthy/the-truth-about-metabolism#:~:text=Your%20metabolism%20increases%20whenever%20you,burn%20protein%20and%20absorb%20it.. Accessed on 12/29/23.