How Metabolism Changes with Age: The Surprising Truth

A new study reveals four distinct phases of metabolic change throughout life and challenges some common myths about metabolism and aging

According to the World Health Organization (WHO), obesity has nearly tripled worldwide since 1975. Obesity is largely affected by your metabolism rate, which is the process by which your body converts food and oxygen into energy and heat. It affects everything from your weight and body temperature to your mood and immune system. You may have heard that your metabolism slows down as you get older, making it harder to lose weight and stay healthy. But is that really true?

According to a new study published in Science, the answer is more complicated than you might think. The researchers measured the energy expenditure of more than 6,000 people from 29 countries and different age groups over a decade. They found that metabolism changes in four distinct phases throughout life: infancy, childhood, adulthood, and old age. And some of these changes are not what you would expect.

We will explain the surprising findings of this research and how they challenge conventional wisdom or logic about metabolism and age. We will also discuss what factors influence metabolism besides age and how you can optimize your metabolism and health at any stage of life.

What is metabolism and why does it matter?

Metabolism is the process by which your body converts food and oxygen into energy and heat. It affects everything from your weight and body temperature to your mood and immune system.

Your metabolism is determined by two main factors: your basal metabolic rate (BMR) and your activity level. Your BMR is the amount of energy your body needs to perform basic functions like breathing, pumping blood, and maintaining cell function. Your activity level is the amount of energy your body uses for physical activities like walking, exercising, or doing chores.

Your metabolism can vary depending on several factors, such as your age, gender, muscle mass, hormone levels, genetics, and environmental factors. Some of these factors are within your control, while others are not.

Why does metabolism matter for your health and aging? Because it influences how many calories you burn and how much fat you store. A higher metabolism means you burn more calories and fat, while a lower metabolism means you burn fewer calories and fat.

A higher metabolism can also help you prevent or manage certain diseases and conditions that are associated with aging, such as obesity, diabetes, cardiovascular disease, osteoporosis, and cognitive decline. A lower metabolism can increase your risk of these diseases and conditions.

Therefore, understanding how your metabolism changes with age can help you optimize your health and well-being at any stage of life.

How does metabolism change with age?

According to a new study published in Science, metabolism changes in four distinct phases throughout life: infancy, childhood, adulthood, and old age. And some of these changes are not what you would expect.

The researchers measured the energy expenditure of more than 6,000 people from 29 countries and different age groups over a decade. They used a method called doubly labelled water, which tracks how much carbon dioxide the body produces by measuring the isotopes of hydrogen and oxygen in urine samples.

They found that metabolism peaks around age 1, when babies burn calories 50 percent faster than adults. Then it gradually declines roughly 3 percent a year until around age 20. This means that teenagers have a higher metabolism than adults, even after adjusting for body size and muscle mass.

From age 20 to 60, metabolism remains stable and does not slow down as commonly believed. This means that middle-aged adults have the same metabolism as young adults, regardless of gender or menopause status.

After age 60, metabolism starts to decline again, by less than 1 percent annually. This means that older adults have a lower metabolism than younger adults, but the difference is not very large.

These findings challenge some of the common myths and assumptions about metabolism and age. For example, many people think that their metabolism slows down significantly after age 30 or 40, or that women have a slower metabolism than men. But this study shows that these are not true.

The researchers also found that the four phases of metabolic change are consistent across different populations and cultures, suggesting that they are driven by biological factors rather than environmental or lifestyle factors.

How does the new study compare with previous studies and assumptions?

The new study is not the first one to investigate how metabolism changes with age, but it is the most comprehensive and diverse one to date. Previous studies have been limited by small sample sizes, narrow age ranges, or homogeneous populations.

A 2001 study by the National Institutes of Health (NIH) measured the resting metabolic rate (RMR) of 757 healthy adults aged 21 to 94. They found that RMR declined by 1 to 2 percent per decade after age 30. However, this study only measured RMR, which is the energy expenditure at rest and does not account for physical activity. It also did not adjust for body composition or other factors that may affect metabolism.

Another example is a 2010 study by the University of Lausanne that measured the total energy expenditure (TEE) of 1,509 Swiss adults aged 35 to 75. They found that TEE declined by 7 percent per decade after age 40. However, this study only included Swiss adults, who may not represent other populations or cultures. It also did not measure energy expenditure directly, but estimated it from self-reported physical activity and body weight.

The new study by Pontzer and colleagues overcomes some of these limitations by measuring energy expenditure directly using doubly labeled water, which is considered the gold standard method. It also includes a large and diverse sample of people from different countries and age groups, ranging from infants to nonagenarians.

The new study challenges some of the common assumptions and myths about metabolism and age, such as:

• Metabolism slows down steadily after age 20. The new study shows that metabolism remains stable from age 20 to 60, and only declines slightly after age 60.
• Women have a slower metabolism than men. The new study shows that after adjusting for body size and composition, there is no significant difference between the metabolic rates of men and women.
• Menopause slows down metabolism. The new study shows that there is no detectable effect of menopause on metabolism, as women’s metabolic rates do not change from age 20 to 60.

The new study also reveals some surprising findings that were not previously known or expected, such as:

• Metabolism peaks around age 1. The new study shows that infants have the highest metabolic rates of any age group, burning calories 50 percent faster than adults.
• Metabolism declines rapidly during childhood. The new study shows that metabolism declines by 3 percent per year from age 1 to 20, which is faster than any other phase of life.
• Metabolism does not vary much among adults. The new study shows that metabolism is remarkably stable from age 20 to 60, regardless of gender or menopause status.

These findings have important implications for understanding how metabolism affects health and disease risk at different stages of life.

How can you optimize your metabolism and health at any age?

But what does this mean for you and your health? How can you optimize your metabolism and well-being at any stage of life?

The good news is that you have more control over your metabolism than you might think. While age is one factor that affects metabolism, it is not the only one. There are many other factors that influence metabolism, such as diet, exercise, hormones, genetics, and environmental factors. And some of these factors are within your control.

Here are some tips and tricks to help you manage your metabolism and health at any age:

Diet. Eat a balanced and nutritious diet that meets your energy needs and supports your health goals. Avoid processed foods, added sugars, and trans fats. Include plenty of fruits, vegetables, whole grains, lean proteins, healthy fats, and water in your diet.

Exercise. Exercise regularly and vary your intensity and type of activity. Aim for at least 150 minutes of moderate-intensity aerobic exercise or 75 minutes of vigorous-intensity aerobic exercise per week. Also include strength training, flexibility training, and balance training in your routine.

Manage Stress. Manage your stress levels and get enough sleep. Stress and sleep deprivation can negatively affect your metabolism, hormones, mood, and immune system. Try to find healthy ways to cope with stress, such as meditation, yoga, breathing exercises, or hobbies. Aim for seven to nine hours of quality sleep per night.

Health checkup. Check your hormone levels and consult your doctor if you have any concerns. Hormones play a key role in regulating metabolism and many other bodily functions. As you age, your hormone levels may change or decline, which can affect your metabolism and health. Your doctor can help you diagnose and treat any hormone imbalances or deficiencies.

Take preventive measures. Know your genetic and environmental factors and take preventive measures. Some people may have genetic or environmental factors that predispose them to certain metabolic disorders or diseases. For example, some people may have a family history of diabetes or thyroid problems. Others may live in areas with high pollution or low sunlight. These factors can affect your metabolism and health in different ways. You can take preventive measures to reduce your risk or manage your condition by following your doctor’s advice and making lifestyle changes.

By following these tips and tricks, you can optimize your metabolism and health at any age. You can also enjoy the benefits of a higher metabolism, such as more energy, better mood, stronger immunity, lower disease risk, and longer lifespan.

Remember that metabolism is not a fixed or static thing. It is a dynamic and complex process that changes throughout life. And you have the power to influence it. So don’t let age or myths stop you from living your best life. Take charge of your metabolism and health today!

Are you tired of scrolling through endless clickbait articles and ads on other platforms? With a Medium membership, you’ll have access to high-quality, ad-free content from top writers and publications. Indulge in the pleasure of reading while supporting the creative work of writers, and take your reading experience to the next level. Sign up now to join the community of readers and writers on Medium