Metabolism refers to all the chemical processes going on inside your body to help sustain life. A key part of the process is converting the food you eat into energy and the products needed to grow and repair the cells in the body.
But metabolism isn’t static and can be influenced by several factors, including exercise and age. As you get older, your metabolism slows and inactivity can cause up to a 5% loss of muscle mass every ten years. In this article, we’ll investigate how exercise and training can impact your metabolism and how they can help improve it as you age.
Body Composition and Metabolism
Body composition is the measurement of everything within your body, including cells, tissues, and organs. It’s commonly split into two:
- Fat mass - all the fat tissues in your body
- Fat-free mass - everything else (muscle, organs, bones, fluid, etc.)
Changes in these components can have several effects on your health. For example, they may lead to weight loss or gain or changes in your metabolism.
What is Basal Metabolic Rate (BMR)?
One way to define and understand your metabolism is through your basal metabolic rate or BMR. Your BMR is the amount of energy or calories your body burns when it is at complete rest. It tells you how much energy you need to carry out essential bodily functions such as breathing, pumping blood, and maintaining your body temperature.
Your muscles are more metabolically active than fat tissue, which means they burn more calories at rest. The reason for this is that muscles contain more mitochondria, the powerhouses of your cells that are responsible for generating energy.
That’s part of the reason why your body composition can have an impact on your metabolism because the more lean muscles you have, the better your metabolic rate will be.
Activities like resistance or strength training are great for increasing your metabolism because they help to build muscle. And the more muscle you have, the higher your metabolism will be.
Factors That Decrease BMR
As we age, our metabolism naturally slows down because of several factors, some of which we can control and others we can’t.
Loss of Muscle Mass
Research shows that a loss of muscle mass is likely responsible for the age-related fall in BMR. We commonly exercise less the older we get, leading to smaller muscles and reduced energy requirements.
On average, after age 30, adults lose 3 to 8% of their muscle mass every decade, which over time, leads to a reduction in strength and increases the risk of falls.
Hormones are another fundamental factor in the age-related reduction of our metabolism. For example, hormones are broken down slower than when we’re younger. Aging is also linked with a decline in anabolic hormones, like testosterone, estrogen, and insulin, which are all involved in the growth and repair of tissues.
This reduction also coincides with other lifestyle factors, such as a natural decrease in physical activity. This can have significant consequences on our energy expenditure, causing it to fall rapidly, resulting in a slower metabolism and an increased rate of obesity in older people.
It’s true that genetics also play a part in our metabolism, which we have very little control over. But there are many things we can do to improve our health, and physical activity is one of those factors.
Exercise’s Impact on Metabolism
Get your sweat on because exercise has some pretty powerful benefits for your metabolism. The more you move, the more calories you burn!
Let’s take a look at some of the different types of training and how they can affect your metabolism.
Aerobic exercise is any type of exercise that provides cardiovascular conditioning or ‘cardio.’ It includes physical activities like:
- Brisk walking
- Yoga and Pilates
Because aerobic exercise requires your body to move and use your muscles more, it increases energy requirements and expenditure. Therefore, aerobic activity temporarily increases your metabolic rate, and it’s really easy to fit into your daily schedule. Just 30 minutes a day is enough to have a positive effect.
A study involving 52 soldiers who participated in an 80-day aerobic and strength exercise program showed the extent of exercise's effects on metabolism. It found that exercise increases the metabolic rate and the amount of fat being burned.
Resistance training involves pushing and pulling your body or muscles against the resistance of an object, but you may be more familiar with the term weight training. It can include activities that use dumbbells, kettlebells, resistance bands, and even your body weight.
But how does resistance training improve metabolism? Weight training increases the amount of lean muscle in your body which is more metabolically active than fat cells. So, if your body has an increased muscle mass, it will require more energy, even if you are resting.
A review by Westcott (2012) demonstrated that weight training consistently increased metabolic rate and lowered fat levels. But that’s not all. Resistance training can improve metabolism by:
- Raising EPOC: After exercise, a natural rise in your metabolism is known as excess post-exercise oxygen consumption (EPOC). After a high-intensity resistance workout, your body needs more energy to restore oxygen levels and repair tissues, which increases calorie burning even after you have finished exercising.
- Improved insulin sensitivity: Resistance training improves the body’s ability to take up glucose from the blood, known as insulin sensitivity. In turn, this improves blood sugar control, helps prevent type 2 diabetes, and positively benefits metabolism by minimizing fat storage.
- Long-term effects: As you age, metabolism naturally slows down. Resistance training has long-term benefits, such as increasing muscle mass over time, which helps you maintain a higher BMR.
Similar to resistance training, HIIT increases the number of calories burned, increases the EPOC effect, and improves insulin sensitivity, all of which are great for metabolism. Further research shows that this type of exercise also boosts metabolism by increasing the number of proteins in skeletal muscle that are essential for energy metabolism.
HIIT has also been shown to have a greater effect on metabolism than running and strength training and could also burn fat for energy rather than carbs.
Additional Factors Affecting Metabolism
Training is just one factor that influences your metabolism. So, it’s important to consider the other lifestyle factors that could positively or negatively affect your BMR.
Stress wreaks havoc on just about every aspect of your life, physically, mentally, socially, and emotionally. When we’re stressed, our bodies release a hormone called cortisol in response, and this can lead to behaviors like craving sugar or eating high-fat foods. Stress can also slow down your metabolism, and all of these factors can contribute to weight gain.
Exercise is critical not only for maintaining a healthy weight and mind but also helps speed up your metabolism. So, if you’re feeling stressed, getting out for a brisk walk, hitting the weights, or getting your heart racing with a HIIT session can have massive benefits.
Many of us need to remember how important restful sleep is. It has so many positive effects, and although it may not have as much of a profound impact as exercise on our metabolism, it’s still a significant contributing factor.
Sleep is associated with many hormonal and metabolic processes, meaning it can contribute to homeostasis. Sleep deprivation can result in:
- Altered blood-sugar metabolism
- Increased appetite
- Reduced energy expenditure
These factors can negatively influence your metabolic rate. But exercise can help you get better sleep, especially moderate to vigorous-intensity activity, making it a win-win for your metabolism and your overall health and well-being.
Your metabolism and what you eat are intrinsically linked. Everything your body does requires energy, even unconscious activities like breathing. And what you put into your body can influence your metabolism, from macros to micros. Even the time you eat has a part to play.
The key to supporting your metabolism from a nutrition perspective is consuming a balanced and nutrient-rich diet. Too much or too little of a specific nutrient is enough to interfere with the metabolic processes taking place in your body.
Exercise is an important factor in supporting our metabolism, but it’s not the only one. There are many different lifestyle elements that contribute to changing and maintaining metabolism, including diet. However, consistent exercise can have profound benefits in boosting our metabolic rate which is especially important as we age.