Aging refers to the physiological changes we experience during our lifespan. It’s also an inevitable part of life.
After all, our cells aren’t made to last forever. The structures and functions in our cells decline over time.
But why does this happen? For decades, scientists have been studying the subject. There are currently more than 300 theories on why we age and experts are learning more every day.
Let’s explore why humans age, and how you can slow down the effects.
Types of aging
Aging can be categorized into two types and due to two types of factors, intrinsic and extrinsic.
Intrinsic aging vs. extrinsic aging
Intrinsic aging is a genetically predetermined process that occurs naturally. Extrinsic aging is a result of outside factors chose by you such as where you live, your stress levels, and your lifestyle habits (like smoking).
Cellular aging
Cellular aging is due to intrinsic factors. It’s related to the biological aging of cells.
Cells are the basic building blocks of the body. Your cells are programmed to divide, multiply, and perform basic biological functions.
But the more cells divide, the older they get. In turn, cells eventually lose their ability to function properly.
Cellular damage also increases as cells get older. This makes the cell less healthy, causing biological processes to fail. Cellular damage accumulates over time, too.
Damage-related and environmental aging
Damage-related and environmental aging is related to extrinsic factors. It refers to how our surroundings and lifestyle affect how we age.
Over time, these factors can damage our cells and contribute to aging.
Everyone experiences both types of aging. However, each form of aging varies from person to person, which explains why we age in different ways.
Theories on aging
It’s generally accepted that aging is caused by multiple processes, rather than one reason. It’s also likely that these processes interact and overlap with each other.
Here are some of the most prominent theories:
Programmed theories of aging
Programmed aging theories say that people are designed to age and that our cells have a predetermined lifespan that’s encoded into our bodies.
Also called active, or adaptive, aging theories, they include:
- Gene theory. This theory suggests that specific genes turn “on” and “off” over time, causing aging.
- Endocrine theory. According to this theory, aging is caused by changes in hormones, which are produced by the endocrine system.
- Immunological theory. Also called the autoimmune theory, this is the idea that the immune response is designed to decline. The result is disease and aging.
Programmed theories have many supporters. However, they suggest that habits linked to longevity, like quitting smoking and exercise, are useless. This is likely inaccurate, as research has continuously proved that these habits affect life expectancy.
Error theories of aging
Error theories, or damage theories, are the opposite of programmed theories. They hypothesize that aging is caused by cellular changes that are random and unplanned.
Error theories of aging include:
- Wear and tear theory. This is the idea that cells break down and become damaged over time. But critics argue that it doesn’t account for the body’s ability to repair.
- Genome instability theory. According to this theory, aging happens because the body loses its ability to repair DNA damage.
- Cross-linkage theory. This theory claims that aging is due to the buildup of cross-linked proteins, which damages cells and slows biological functions.
- Rate-of-living theory. Proponents of this theory say that an organism’s rate of metabolism determines its lifespan. However, the theory lacks solid and consistent scientific evidence.
- Free radical theory. This theory suggests that aging is due to the buildup of oxidative stress, which is caused by free radicals. But some say this theory fails to explain other types of cellular damage seen in aging.
- Mitochondrial theory. As a variation of the free radical theory, this theory says that mitochondrial damage releases free radicals and causes aging. The theory lacks hard scientific evidence.
Genetic theory of aging
The genetic theory proposes that aging primarily depends on genetics. In other words, our life expectancy is regulated by the genes we got from our parents.
Since genes have predetermined traits, it’s thought this theory overlaps with programmed theories of aging.
Genetic theories include:
- Telomere theory. Telomeres protect the ends of your chromosomes as they multiply. Over time, telomeres shorten, which is associated with disease and aging.
- Programmed senescence theory. Cellular senescence occurs when cells stop dividing and growing but don’t die. This theory suggests that this causes aging.
- Stem cell theory. Stem cells can turn into other cells, which helps repair tissue and organs. But the function of stem cells declines over time, potentially contributing to aging.
- Longevity gene theory. This is the idea that certain genes extend lifespan. More research is necessary.
The limitation of genetic theories is that they disregard the importance of external factors. In fact, it’s estimated that just 25 percent of lifespan is influenced by genetics. This suggests that environmental and lifestyle factors play a major role.
Evolutionary theory of aging
Natural selection refers to the adaptive traits of an organism. These traits can help the organism adjust to their environment, so they’re more likely to survive.
According to evolutionary theories, aging is based on natural selection. It says that an organism begins aging after they have reached their peak of reproduction and have passed down adaptive traits.
Evolutionary theories include:
- Mutation accumulation. This theory presumes that random mutations accumulate later in life.
- Antagonistic pleiotropy. According to this theory, genes that promote fertility early in life have negative effects later on.
- Disposable soma theory. The theory claims that when more metabolic resources are directed towards reproduction, the less is put towards DNA repair. The result is cell damage and aging.
These theories are still being researched and require more evidence.
Biochemical theory of aging
Another theory is that biochemical reactions cause aging. These reactions occur naturally and continuously throughout life.
This theory is rooted in various concepts, including:
- Advanced glycation end products (AGEs). AGEs develop when fats or protein are exposed to sugar. High levels may lead to oxidative stress which speeds up aging.
- Heat shock response. Heat shock proteins protect cells from stress but their response decreases as we age.
- Damage accumulation. Normal chemical reactions damage DNA, proteins, and metabolites over time.
Why do life expectancies increase?
In recent decades, life expectancy around the world has increased. This is due to many factors including:
- better nutrition
- improved hygiene
- access to health care
- improvements in modern medicine
These factors can protect our cells and reduce cellular damage, increasing life expectancy.
Why do women live longer than men?
In most parts of the world, women live longer than men. This is due to several biological, social and environmental factors.
Women, on average have more estrogen than men. Estrogen is the female sex hormone. It’s been found to have anti-inflammatory and immune-boosting effects, which may protect women from certain diseases.
In contrast, the male sex hormone testosterone may suppress the immune system. Men typically have more of this hormone.
Can we slow the effects of aging?
Though aging is inevitable, it’s possible to slow down some of the effects. You can do this by following healthy lifestyle habits.
Here’s how to slow aging:
- Eat a nutritious diet. Focus on fruits, vegetables, whole grains, and lean protein. Limit processed foods.
- Stay active. Exercise reduces the physical and mental effects of aging. Aim for 30 minutes a day, 5 days a week.
- Avoid tobacco. Tobacco speeds up aging. Quitting is often difficult but a doctor can help create a cessation plants that work for you.
- Drink alcohol in moderation. Alcohol increases your risk of chronic disease.
- Attend regular checkups. Routine checkups with a doctor are the best way to prevent or treat disease early.
- Know your family history. Discuss your family’s health history with your doctor to have appropriate screening or get early treatment for potential chronic diseases.
- Engage your brain. Protect your cognitive function by doing brain exercises.
- Wear sunscreen. Sunscreen protects your skin from UV radiation which can lead to premature aging.
Takeaway
Aging is likely caused by a combination of reasons. Some theories suggest cells have a predetermined lifespan while others claim it’s caused by error and damage. Other theories say that aging is due to genetic, evolution, or biochemical reactions.
Aging is normal but following a healthy lifestyle may help you live longer. Habits like eating well, exercising regularly, and wearing sunscreen can reduce your risk of disease and improve your quality of life.
Chronological Aging and Biological Aging
When asked how old you are, you likely answer based on the number of years that have passed since you were born. That would be your chronological age.
But maybe your doctor says you have the physical conditioning of a 21-year-old. This would be considered your biological age, regardless of how many years ago you were born.
Your chronological age will always be an easy-to-determine number while your biological age depends on a number of variables that can change on a continuing basis.
The difference between the two can be surprising and definitely worthy of further exploration.
What is chronological aging?
Your chronological age is the amount of time that has passed from your birth to the given date. It’s your age in terms of years, months, days, etc. This is the primary way people define their age.
It’s also a primary risk factor for chronic diseases, mortality and any impairment to bodily functions such as hearing and memory.
What is biological aging?
The basic idea behind biological aging is that aging occurs as you gradually accumulate damage to various cells and tissues in the body.
Also known as physiological or functional age, biological age differs from chronological age because it takes into consideration a number of factors other than just the day you were born.
The actual number comes down to different biological and physiological development factors. Some of these include:
- chronological age
- genetics (for example, how quickly your body’s antioxidant defenses kick in)
- lifestyle
- nutrition
- diseases and other conditions
Using these guidelines along with various mathematical models, medical professionals can figure out what age your body “acts” like it is.
While chronological age is a factor, you may not end up having the same biological age as your chronological age.
For example, if you’re a 28-year-old male who doesn’t exercise, only eats high-fat foods, and has smoked five packs of cigarettes per day for the last 10 years, it’s likely you would have a biological age of greater than 28 years.
How to age healthily
You can take numerous steps to try to improve your biological age. Starting at any age can help. Here are some of the ways you can healthily age:
Exercise or engage in physical activity
Everybody, especially those with high blood pressure, diabetes, heart disease or arthritis can benefit from regularly exercising.
For younger adults, exercise improves the amount of blood the heart can pump with each beat (stroke volume) and lowers resting heart rate.
Exercise helps older adults have better heart and lung function, which can increase endurance and reduce fatigue.
Types of exercises to try include the following:
Balance exercises reduce the risk of falling, which is a major cause for injuries in elderly adults.
Strength exercises help build muscle mass, which reduces the risk of osteoporosis later in life.
- Endurance exercises help your breathing and heart rates rise, which on a regular basis improves lung and heart health and stamina, as well as benefiting your circulatory system. Examples of endurance exercises are swimming, walking and biking.
- Stretching keeps your body loose, which allows you to continue doing everyday tasks with minimal aches and pains.
Maintain a healthy weight
Overweight individuals have a higher risk of high blood pressure, heart disease, diabetes, certain forms of cancer, and more.
However, being thinner doesn’t mean you are necessarily healthier. It could be the result of increased frailty or another underlying condition.
Maintain a healthy shape
In addition to weight, the way your body distributes fat is very important for healthy aging. This is usually determined by your waist-to-hip ratio and waist circumference.
- Pear-shaped bodies. Fat accumulates on the outer edges, such as your hips and thighs. This is the sign of a healthy body fat distribution.
- Apple-shaped bodies. Fat shifts from the outer edges to the abdomen and waist, which can increase the chance of heart disease and breast cancer.
Eat more foods with a low glycemic index value
The nutrients in these types of food help keep your bones, muscles and organs strong for long periods of time.
Examples of these foods include fruits, vegetables, beans, low-fat dairy, and high-fiber (whole-grain) breads. Try adding these to your diet.
Additionally, reduce the amount of fast food, white bread, and soda that you consume as these can cause an unhealthy increase in blood sugar.
Be aware of the nutrients in the foods you eat
Although more studies need to be done on factors for determining biological age, research has shown that there is a clear link between nutrition and your biological age.
Being actively aware of what constitutes a healthy diet and consulting nutrition labels when making food purchases may help improve your biological age.
The takeaway
Your chronological age will always increase at a set rate as the years pass. However, there are steps you can take to improve your biological age. With the right lifestyle changes, you could even have a younger biological age than your chronological age.
