Metabolism is the sum of all the chemical reactions that take place in your body to keep you alive and functioning. These reactions utilize the energy from the foods you eat. The more calories your body burns each day while performing various physiological and physical functions, the higher your metabolism is and vice versa. As you get older, you have to be more and more cautious about what you eat. You cannot continue to eat the foods you used to when you were a teen when you are well into your 30s or more. This is because, as you age, your metabolism slows down, making it much easier to gain those extra unwanted pounds than to lose them.
The rate of your metabolism is dependent on factors like your resting metabolic rate, which is the number of calories you burn while you are resting or sleeping; the thermic effect of food, which is the number of calories burned when you digest and absorb food; the number of calories burned through exercise; and the number of calories you burn when you engage in non-exercise activities, such as standing, sitting, fidgeting, or doing household chores. Here are some of the reasons why your metabolism decreases as you age.
You Tend To Be Less Active As You Age
Your activity levels significantly influence your rate of metabolism. Both exercise and non-exercise activities you perform on a daily basis account for almost 30 percent of the calories you burn on a daily basis. For those people who are extremely active, this number can go as high as 50 percent.1 But unfortunately, as you age, you tend to become less and less active, especially once you reach the age of 50 and more. This can cause a dramatic decrease in your rate of metabolism. So even if you get older, you should not slow down. Try and exercise as much as you can and as much as your health allows you to in order to keep your metabolism high.2
Your Metabolic Processes Slow Down With Age
The number of calories you burn when you are sleeping or resting, your resting metabolic rate, is determined by the chemical reactions that occur inside your body. These reactions are driven by your sodium-potassium pumps and your mitochondria.34 As you age, these components of your body lose their efficiency, which results in the decrease in your metabolism. The sodium-potassium pumps in individuals older than 25 are almost 18 percent slower than individuals who are younger.5 Adults around the age of 60 to 70 also have 20 percent fewer mitochondria than younger individuals around the age of 25 to 30 do. In addition to this, the mitochondria of older adults are nearly 50 percent less efficient in using oxygen for energy, which is a crucial process that helps regulate your metabolism.6
You Lose Muscle With Age
An average person loses about 3 to 8 percent of their muscle during each decade after 30. By the time you reach the age of 80, you have about 30 percent less muscle than you did when you were 20.7 This loss of muscle is known as sarcopenia and it increases your chances of fractures, weakness, and even early death. Since the amount of muscle you have greatly influences your resting metabolism rate, sarcopenia results in the slowing down of your metabolism.8You can improve your muscle mass by being more active, engaging in strength training once or twice a week, and by increasing your protein consumption.
|↑1||von Loeffelholz, Christian. “The role of non-exercise activity thermogenesis in human obesity.” 2014.|
|↑2||Van Pelt, Rachael E., Pamela P. Jones, Kevin P. Davy, Christopher A. DeSouza, Hirofumi Tanaka, Brenda M. Davy, and Douglas R. Seals. “Regular exercise and the age-related decline in resting metabolic rate in women.” The Journal of Clinical Endocrinology & Metabolism 82, no. 10. 1997.|
|↑3||Larsen, Filip J., Tomas A. Schiffer, Kent Sahlin, Björn Ekblom, Eddie Weitzberg, and Jon O. Lundberg. “Mitochondrial oxygen affinity predicts basal metabolic rate in humans.” The FASEB Journal 25, no. 8. 2011.|
|↑4, ↑5||Poehlman, E. T., MICHAEL J. Toth, and GEORGE D. Webb. “Sodium-potassium pump activity contributes to the age-related decline in resting metabolic rate.” The Journal of Clinical Endocrinology & Metabolism 76, no. 4. 1993.|
|↑6||Conley, Kevin E., Sharon A. Jubrias, and Peter C. Esselman. “Oxidative capacity and ageing in human muscle.” The Journal of physiology 526, no. 1. 2000.|
|↑7||Frontera, Walter R., Virginia A. Hughes, Roger A. Fielding, Maria A. Fiatarone, William J. Evans, and Ronenn Roubenoff. “Aging of skeletal muscle: a 12-yr longitudinal study.” Journal of applied physiology 88, no. 4. 2000.|
|↑8||Walston, Jeremy D. “Sarcopenia in older adults.” Current opinion in rheumatology 24, no. 6. 2012.|