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Metabolism is the sum of all the chemical processes in your body to digest and absorb nutrients from food to sustain life. This complex system includes total energy expenditure (TEE), the sum of basal metabolic rate (BMR), energy used for physical activities, and energy used to digest food.

Author

Glenn R. Moore

Reviewed by

Dr. Robert Stevens, MD.

Date

July 23, 2024

Category

Health and wellness

Tags

Immunity, Lifestyle, Longevity

The Truth About Metabolism: What You Need to Know

Immunity, Lifestyle, Longevity

Reviewed by

Circle check iconMedically reviewed by Dr. Robert Stevens, MD. - Written by Glenn R. Moore on July 23, 2024

July 23, 2024

Glenn R. Moore

As we age, our metabolism changes – we gain weight and lose energy. We will explain why metabolism slows down with age and how to keep your metabolic rate healthy.

Quick Facts

  • Metabolism doesn’t decline from early adulthood, it peaks at 1 year old, declines until 20, stabilizes and then declines again after 60.
  • Maintaining muscle mass is key to metabolic health. Muscle tissue burns more calories than fat, even at rest. Strength training and muscle-building activities will help preserve muscle mass and boost metabolism, as we age.
  • Dietary strategies, such as adequate intake of protein and whole grains, in addition toregular physical activity, like high intensity interval training (HIIT), will support a healthy metabolism and counteract age-related metabolic decline.

Metabolism and Aging

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Metabolism is the sum of all the chemical processes in your body to digest and absorb nutrients from food to sustain life.

This complex system includes total energy expenditure (TEE), the sum of basal metabolic rate (BMR), energy used for physical activities, and energy used to digest food.

Total daily energy expenditure (TDEE) is the total calories your body uses daily and is influenced by body composition.

Metabolism follows a specific pattern throughout our lives:

  • Peaks at 1year old
  • Declines until 20 years old, then stabilizes
  • Remains stable until 60 years old
  • After 60 years old, it declines but at a rate of less than 1% per year

So, for most of our adult life, our metabolic rate is stable, not declining from early adulthood, as we are often told.

However, age-related changes in physical activity, tissue-specific metabolism, and body size impact total energy expenditure at different life stages.

In early life, tissue-specific metabolism is higher, so energy needs are higher; in later life, metabolism is slower so energy expenditure is lower,.

To support metabolic health throughout the human life course, we need to understand these changes.

Why Metabolism Slows Down Over Time

Natural loss of muscle mass, which can start as early as 30, is one of the main reasons metabolism slows down with age.

This process is called sarcopenia and can result in a 3-5% loss of muscle mass per decade.

By 40, this muscle loss accelerates and is replaced by fat, further slowing it down.

A slow metabolism occurs when you burn fewer calories at rest because of the loss of muscle mass.

Decreased physical activity also plays a big role. Older adults are less active, contributing to muscle loss and directly affecting the number of calories burned through physical activity.

Muscle loss and reduced activity result in lower metabolic rate and energy expenditure. Hormonal changes, such as lower testosterone and estrogen levels, also worsen this decline.

While genetics play a role in muscle size and the ability to build muscle, their impact on metabolism is smaller than that of lifestyle factors.

Changes in sodium-potassium pumps and mitochondria are present but have a minimal effect on overall metabolism compared to muscle loss and reduced physical activity.

Muscle Mass and Metabolism

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A higher metabolism is mainly due to the role of muscle mass.

More muscle mass means a higher metabolic rate, as muscles require more energy than fat.

That’s why strength training and other muscle-building activities are key to boosting metabolism and burning more calories at rest.

As we age, preserving muscle mass for both men and women cannot be emphasized enough.

Preserving muscle mass has many benefits.

It prevents weight gain, supports overall metabolic health, improves balance, reduces the risk of falls, and helps maintain mobility.

Focusing on muscle health and fat-free mass can reverse many of the declines in metabolism and energy expenditure that occur as we age.

Importance of Preserving Muscle Mass

Sufficient muscle is needed to perform daily activities and live independently.

Without enough muscle strength, tasks that were once easy can become difficult and impact your quality of life.

Perform muscle strengthening exercises at least twice weekly to preserve and build muscle mass to support higher metabolism and better health.

Effective Strength Training Exercises

Preserving and building muscle mass requires effective strength training exercises like pushups and squats.

These exercises target major muscle groups and provide the necessary resistance to stimulate muscle growth.

Customizing weight-bearing exercises to individual ability levels ensures they are safe and effective.

Resistance training or weight lifting is especially effective for increasing resting metabolic rate (RMR) in older adults.

Hormonal Changes and Metabolism

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For women, menopause leads to lower estrogen hormone levels, which can slow down metabolism and lead to weight gain.

Men experience a decline in testosterone levels, which also affects muscle mass and body composition changes, which impact metabolic rate.

The thyroid gland, which produces hormones that regulate metabolism, may become less efficient with age.

The adrenal cortex hormone aldosterone, which helps maintain fluid and electrolyte balance, also decreases with age.

Although cortisol levels in the blood do not decrease, they can still impact metabolic health by influencing appetite and fat storage.

Stress and sleep quality are also key factors.

Chronic stress triggers cortisol release, which can increase appetite, promote fat storage, and negatively impact metabolism.

Poor sleep quality disrupts hormonal balance and contributes to metabolic decline.

Addressing these hormonal changes through lifestyle changes can help maintain a healthy metabolism.

Dietary Strategies to Support Metabolism

Adequate protein intake is crucial for preserving muscle mass and preventing metabolic decline.

Protein-rich foods have a higher thermogenic effect, meaning they require more energy to digest, which can help boost metabolism.

Besides protein, whole grains play a big role.

They are rich in fiber and nutrients, which help regulate blood sugar levels and support essential functions.

Additionally, avoid late-night eating as it can increase hunger signals, decrease leptin levels, and slow down calorie burn.

By incorporating these dietary strategies, you can have a stable and efficient metabolism.

Adequate Protein Intake

Older adults need 0.45 to 0.55 grams of dietary protein per pound of body weight to maintain muscle and bone health.

More protein can help reduce muscle loss associated with aging, also known as age-related sarcopenia.

High protein intake can boost metabolism and burn more calories per day.

Eating enough protein is also important during weight loss as it helps preserve muscle mass while reducing body fat.

Including lean protein sources can improve overall health and support weight.

Salmon, poultry, eggs, nuts, seeds, and soy (such as tofu) are all good sources of protein.

Balanced Diet and Whole Grains

Whole grains are rich in B vitamins, iron, and magnesium, which are good for overall health.

Choose whole grains over refined grains to get more health benefits and prevent blood sugar crashes.

Including nutrient-dense foods in your diet not only helps maintain metabolic function but also provides essential fatty acids.

Eat foods like whole grains, fruits, vegetables and fiber.

These foods support metabolic health by keeping the body fueled longer and preventing decline.

Physical Activity and Metabolic Health

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Exercises like high-intensity interval training (HIIT) are particularly effective in boosting metabolism.

Moderate physical activity is also important for older adults to manage obesity, heart disease, and diabetes.

By keeping active, you can maintain a healthy weight, preserve muscle mass, and support overall metabolic health.

Benefits of High-Intensity Interval Training (HIIT)

High-intensity interval Training (HIIT), which is an workout, can boost metabolic rate by creating an ‘afterburn effect.’

This means muscles need more energy to recover after exercise and burn calories longer after the exercise is done.

Research shows HIIT can burn up to 190 calories, 14 hours post-exercise, making it a powerful tool to boost metabolism.

HIIT not only burns more calories but also builds and preserves muscle mass, which is important in combating a slowing metabolism as we age.

HIIT can also increase insulin sensitivity and increase the amount of proteins in your muscles which are important for muscle contraction and energy metabolism.

It also increases oxygen consumption.

Incorporating HIIT into your fitness routine can support both metabolic health and overall physical fitness.

Just be sure you have plenty of time in between for your body to recover.

Regular Exercise

Being active can help older adults avoid metabolic syndrome and insulin resistance, which are associated with aging.

Walking, water aerobics, dancing, or even pushing a lawnmower are good for maintaining muscle mass in older adults.

Setting a realistic goal, such as three 15-minute walks per week, can help you stay consistent with exercise.

Before starting any new exercise program, consult a healthcare provider to ensure safety and get personalized exercise advice.

This is more important for older adults or those with preexisting health conditions.

Lifestyle Factors that Affect Metabolism

Metabolism is greatly affected by several lifestyle factors, including age, gender, sleep, and stress management.

Non-exercise activity thermogenesis (NEAT), which includes calories burned through activities other than exercise or resistance training, accounts for a large portion of daily energy expenditure.

Older adults burn 29% fewer calories through NEAT, so they may need to adjust their activity level or calorie intake.

Sleep

Lack of sleep can slow down metabolism, and getting adequate sleep can reverse it.

With 4 hours of sleep, metabolism decreased by 2.6% compared to 10 hours of sleep.

This shows how much sleep duration affects metabolism.

Sleep deprivation can also increase cortisol levels, leading to a slower metabolism.

Older adults still need 6-7 hours of sleep each night, which is a bit less than younger adults.

Good sleep quality and duration help maintain hormonal balance and reduce the risk of metabolic disorders and overall health.

Stress Management

Managing the metabolic consequences of chronic stress requires stress management.

Prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis due to stress can lead to metabolic problems like obesity and type 2 diabetes.

Effective stress management techniques like mindfulness, meditation, and regular physical activity can reduce these metabolic disturbances.

It's also important to stay hydrated and eat a balanced diet.

For older adults, time spent with others can also be a way to de-stress.

In addition, spending time with animals has been shown to be a great stress reliever!

By incorporating stress management into daily life, individuals can improve overall metabolic health and reduce the risk of stress-related metabolic disorders.

Myths About Aging and Metabolism

There are several myths about aging and metabolism. One is that weight gain is inevitable with age.

While most adults gain 1-2 pounds yearly from 40 to 65, it doesn’t mean weight gain is unavoidable.

Hormones play a role in this as well, so it's good to have them checked.

Another myth is that metabolism slows down uniformly across all ages.

However, a study on women of all ages found no significant difference in resting metabolic rate (RMR) among different age groups; thus, metabolism doesn’t slow down equally.

Restrictive diets, such as calorie-restricted diets, can also slow down metabolism, telling the body to conserve energy by slowing down the metabolic process.

Understanding individual variation in energy expenditure is key to achieving and maintaining a healthy weight throughout life.

Preventive measures for healthy metabolism

Exercising regularly, strength training, and adequate protein intake are essential to maintaining a healthy metabolism.

Staying hydrated, getting enough sleep, adjusting eating habits, and staying physically active can also help seniors maintain a healthy weight and prevent metabolic decline.

Adding green tea to your diet can boost metabolism due to its caffeine and plant compounds.

Drinking green tea can increase metabolism by 4-5%, making it a simple and effective addition to a healthy lifestyle.

Frequently Asked Questions

Does metabolism slow down with age?

Yes, metabolism slows down with age due to muscle loss, decreased physical activity, and hormonal changes. These factors contribute to the natural decline in metabolic rate as we age.

How do I maintain my metabolism as I age?

To maintain a healthy metabolism as you age, focus on exercise, adequate protein intake, stress management, and obtaining sufficient sleep. These can support your body’s metabolic health.

Are there exercises that boost metabolism?

Yes, strength training and high-intensity interval training (HIIT) effectively boost metabolic rate and preserve muscle mass. Add these to your routine to increase your metabolism.

How does sleep affect metabolism?

In summary, sleep is key to hormonal balance and metabolic function; sleep deprivation slows down metabolism and increases appetite.

Can diet change my metabolism?

Yes, adding protein and whole grains to your diet can support metabolic health by preserving muscle mass and stabilizing blood sugar. This is science.

Reviewed by

Circle check iconMedically reviewed by Dr. Robert Stevens, MD. - Written by Glenn R. Moore on July 23, 2024

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