Written by Monica Mollica

Everybody wants to stay young and vital throughout life. But aging is topic surrounded by many questions and myths; here we’ll get to the bottom of it.

Different types of Aging – Chronological Aging and Physiological Aging

Before we get started, I want to make a distinction of two types of aging; chronological and physiological (or biological).

Chronological age is based on time and is the same for everyone who is born on the same date. It refers to age in number of years.

Physiological age, also called biological age, is the result of many factors, many of which are under your control, and varies from person to person (even if they were born on the same date). It refers to age in terms of physical capacity.

Chronological aging refers to how long you have been alive, and is determined by a mathematical formula that is the same for everybody: current date minus date of birth. It is a function of time and cannot be slowed, stopped or accelerated (a side note: according to Einstein’s Theory of Relativity, chronological can be modified, since as one approaches the speed of light, time slows down, and thus so does chronological age. But this isn’t relevant for us earthbound folks).

Physiological aging, on the other hand, describes the state of your body. What’s interesting with physiological aging is that many of the factors that impact it are under your full control (e.g. exercise, nutrition, sleep etc). While chronological and physiological aging are related, the years of your life doesn’t necessarily have much to do with the years of your body. Many people don’t like to tell their (chronological) age; however, if you have taken care of yourself you should be proud of it!

Thus, chronological age and physiologic age do not always coincide, and physical appearance and health status often do not always correspond to what is typical at a particular chronological age. When talking about aging and anti-aging, it is the physiological age we’re referring to. Ok, now that we got that cleared out, let’s move on.

Primary and Secondary Aging

Aging can also be conceptualized as the result of two interactive and overlapping processes, known as primary and secondary aging 1. However, this theory is not universally accepted because it is hard to completely separate each factor.

Primary aging, or “intrinsic senescence,” is the progressive deterioration in physical structure and biological function that occurs with advancing age alone, independent of other factors. For example, changes in body composition (ie, decreased bone mineral density, decreased muscle mass, and abdominal fat accumulation) 2-4 and progressive decline of cardiac, pulmonary, renal, and immune function occur normally with increasing age 5-7.

Secondary aging is the accelerated deterioration in organ structure and function that is mediated by diseases, such as diabetes and hypertension, or by harmful environmental and lifestyle factors, such as tobacco smoking or excessive sun exposure 8-10.

Definition of Aging

All humans and animals (and other living organisms as well for that matter) undergo changes with time. As a multidimensional reality of life, aging is difficult to define simply. The National Institute on Aging states that “in its broadest sense, aging merely refers to changes that occur during the lifespan”. The World Health Organization (WHO) defines aging as a “process of progressive change in the biological, psychological and social structure of individuals’. Yet another definition is “the lifelong process of growing older at cellular, organ, and whole-body level throughout the life span” 11.

From a biological standpoint, aging is often used synonymously with the term senescence, defined as “a biological process of dysfunctional change by which organisms become less capable of maintaining physiological function and homeostasis 12.

Thus, aging can be viewed as a decline, change or development. A decline in body and mental functions has a negative connotation. A change in body and mental functions is neutral in meaning. However, not all aspects of aging decline with age. Our ability to love and be loved does not diminish; at the beach we might pick up grand-kids instead of sweethearts, but our capacity for joy is undiminished. As we will see below, a third view of aging is that of further development. Like age itself, experience, knowledge and wisdom can only increase with time.

One of the reasons for the lack of a singular definition of aging is that it can be considered in so many different ways, according to social, behavioral, physiological, morphological, cellular and molecular changes and norms. Research has led to a number of theories being proposed that may explain the aging process.

Theories of Aging

I want to make it clear right from the start that the ultimate causes of aging remain unknown. The aging process is complex and multifactorial. However, intense research over the past decades has culminated in several theories of aging 13 14. These theories of aging can be categorized into different levels: evolutionary, molecular, cellular and systemic (whole body). The table below summarizes these theories and gives a brief description of each.

Classification and brief description of main theories of aging

Biological Level/Theory



Mutation accumulation

Mutations that affect health at older ages are not selected against.

Disposable soma

Somatic cells are maintained only to ensure continued reproductive success; after reproduction, soma becomes disposable.

Antagonistic pleiotropy

Genes beneficial at younger age become deleterious at older ages.

Pleiotropy refers to a single gene that affects multiple physiological traits.


Gene regulation

Aging is caused by changes in the expression of genes regulating both development and aging.

Codon restriction

Fidelity/accuracy of mRNA translation is impaired due to inability to decode codons in mRNA.

Error catastrophe

Decline in fidelity of gene expression with aging results in increased fraction of abnormal proteins.

Somatic mutation

Molecular damage accumulates, primarily to DNA/genetic material.


Gradual accumulation of random molecular damage impairs regulation of gene expression.


Cellular senescence-Telomere theory*

Phenotypes of aging are caused by an increase in frequency of senescent cells.

Senescence may result from telomere loss (replicative senescence) or cell stress (cellular senescence).

Free radical

Oxidative metabolism produces highly reactive free radicals that subsequently damage lipids, protein and DNA.


Accumulation of normal injury.


Programmed cell death from genetic events or genome crisis.



Alterations in neuroendocrine control of homeostasis results in aging-related physiological changes.


Decline of immune function with aging results in decreased incidence of infectious diseases but increased incidence of autoimmunity.


Assumes a fixed amount of metabolic potential for every living organism (live fast, die young).

Don’t worry if you don’t understand all the terms in the table; I put it here just as a demonstration and summary of the different aging/anti-aging research domains.

The major theories of aging are all specific of a particular cause of aging, providing useful and important insights for the understanding of physiological changes occurring with aging. While proponents of any specific theory might state that their theory is the “one and only”, it should be noted that there is a lot of overlap between them. Alterations of molecular events with aging may lead to cellular alterations, and these, in turn, contribute to organ and systemic failure with evolutionary implications for reproduction and survival.

Thus, the search for a single cause of aging (such as a single gene or the decline of a single body system) has recently been replaced by the view of aging as an extremely complex, multifactorial process 15. In fact, it is very likely that several processes simultaneously interact and operate at different levels of the functional organization 16. In complex, multicellular organisms like humans and animals, the study of interactions among intrinsic (genetic), extrinsic (environmental), and stochastic (random damage to vital molecules) causes provides a more fruitful global approach conducive to a comprehensive and realistic understanding of the aging process. Therefore, different theories of aging should not be considered as mutually exclusive, but may be complementary of others to explain some or all the features of the normal aging process.

As the different theories of aging show, a great deal of the aging process is understood. In several animal species (rodents, monkeys), experimental interventions show that it is possible to delay the onset of functional decline and pathology, and to prolong the life span by manipulating molecular (e.g., free radical reduction), cellular (e.g., mitochondrial protection), and systemic (e.g., endocrine shifts) mechanisms 17. And recent progress in anti-aging research shows exciting promising applications for therapeutic human interventions 18-22. I will cover this in detail in part two of this article.

Usual “Normal” Aging and Successful Aging

Many people see aging as a time of cognitive and physical decline. For the past three decades, the general public and most scientists and have accepted this negative age-stereotype as the norm 23 24. The elderly have been viewed and labeled as, ‘ill and/or disabled’, impotent’, ‘ugly’, ‘mentally declining’, ‘mentally ill’, ‘useless’, ‘isolated’, ‘poor’ and ‘depressed’. This negative stereotyping of and discrimination against people because they are old is known as “ageism” 23.

Studies of human aging in the 1960s to 1980s focused on average “normal” age-related functional losses with aging in organs and systems of the body 25. While it is true that bodily functions degrade as we get old, we have all seen people who look younger and are more capable than their peers. This has even been scientifically documented 26 27. The traditional aging research totally neglected this, despite evidence that there are substantial functional differences of older person within the same age groups. Differences in functionality within age groups were simply attributed to genetic endowment. Although genetic factors contribute to the way we age, and is a field of research on its own 28, our genes still only account for a minor part of how gracefully we age. Twin studies that examined the influence of genes on aging have shown that heritability explains about 20-30% of differences in lifespan, and 22% of differences in functioning 29. Both longevity and functioning appear less heritable than cognitive ability 30. Thus, most of the differences between how gracefully we age stem from non-heritable influences of peoples environment and lifestyle, which are not part of the aging process.

Thankfully, in the 1980s and 1990s the view of aging started to shift and challenged the inevitability of functional impairment and of disease in the elderly 31 32. This new view of aging groups the aging processes into three possible paths 31 32:

  1. Aging, with disease and disability.
  2. Usual aging, with the absence of overt pathology, but with the presence of some declines in function.
  3. Successful (or healthy) aging, with little or no pathology and little or no functional loss.

Such a grouping of aging processes de-emphasizes the view that aging is exclusively characterized by declines in functional competence and health, and re-focuses on the substantial heterogeneity among old persons. It also underscores the existence of positive outcomes (i.e. without disability, disease, or major physiological decline), and highlights the possible avoidance of many, if not all, the diseases and disabilities usually associated with old age.

According to the new perspective on aging, mechanisms of successful aging consist of:

  1. Persistence of normal function.
  2. Compensatory responses induced by exercise, good nutrition, and education to restore function.
  3. Interventions to replace deficient function (as represented by replacement therapies).
  4. Changing of health outcome by modifying risk profiles.
  5. Prevention of disease.
  6. Strengthening of social interactions.

With this new aging perspective, the traditional meaning of life span has been replaced by health span.

Successful Aging – what’s in a name?

While the concept of successful aging is popular among both scientists and the general population, there is no one single agreed upon definition for it. There’s even no agreement on the term to be used, with descriptors ranging from successful aging to healthy aging, productive aging, active life expectancy, healthy years, and aging well 31 33-37.

According to the classic definition 31 32 38, successful aging can be characterized as involving three components:

  1. Freedom of disease and disability.
  2. High physical and cognitive functioning
  3. Social and productive engagement.

Later refinements to the definition have added psychosocial aspects to the definition, such as self-acceptance, positive relations with others, autonomy, environmental control, purpose in life, and personal growth 39. It has also been suggested that successful aging is a developmental process that can be achieved at any stage in the life span 39.

Regardless what criteria and what terms we use, we all want to have the capacity to thrive and prosper for as long as we live.

Lifespan, healthy life expectancy and longevity

Let’s take a look at some aging trends and projections.

The average lifespan of humans has increased over the past century, mainly a result of a significant improvement in sanitary conditions, public health reforms and improved personal hygiene, advances in medical knowledge and practices, and living standards 40. The average life expectancy at birth is now approximately 75 years in males, and 80 years in females in the USA (World Health Organization 2003). This can be compared to 48 years at the beginning of the 1900s 40.

In the United States, the population aged 65 and older was 3.1 million (4% of the total population) in 1900, in 1950, this number had increased to 12.2 million (8.1% of the total population), and in 2000 it grew to 35 million (12.4% of the total population) 41.  In 2008, 39 million people age 65 and over lived in the United States, accounting for 13 percent of the total population.

The older population grew from 3 million in 1900 to 39 million in 2008. The oldest-old population (those age 85 and over) grew from just over 100,000 in 1900 to 5.7 million in 2008. The baby boomers (those born between 1946 and 1964) will start turning 65 in 2011, and the number of older people will increase dramatically during the 2010–2030 period. The older population in 2030 is projected to be twice as large as their counterparts in 2000, growing from 35 million to 72 million and representing nearly 20 percent of the total U.S. population 41.  The oldest-old population is projected to grow rapidly after 2030, when the baby boomers move into this age group. The U.S. Census Bureau projects that the population age 85 and over could grow from 5.7 million in 2008 to 19 million by 2050. Some researchers predict that death rates at older ages will decline more rapidly than is reflected in the U.S. Census Bureau’s projections, which could lead to an even faster growth of this population 42-44.

In 2000, the World Health Organization recognized that quality of life in old age is as important as increased longevity, and introduced the concept of healthy life expectancy (also called HALE), defined as the “average number of years that a person can expect to live in ‘full health’ by taking into account years lived in less than full health due to disease and/or injury” (World Health Organization 2000). A simpler way of saying this is that the healthy life expectancy is the number of years an individual is expected to live without any major debilitating diseases (World Health Organization 2000). The healthy life expectancy is about 67 years for males and 71 years for females (World Health Organization 2000).

The maximum observed lifespan represents the longest-lived member(s) of the population 45. In humans, the oldest individual ever recorded was a woman, who died in 1997 in France at the age of 122 years 46. The oldest recorded man  died in 1998 at the age of 115 47. By contrast, the average lifespan (or life expectancy at birth) refers to how long people live on average in a given population 40. The theoretical maximum lifespan, or potential maximum lifespan,  is the theoretical highest attainable age 45. Today, we don’t know what age this is, but it has been speculated to be around 125 years 48.

Do we have an immutable life span limit?

A fundamental question in aging research is whether humans possess an immutable life span limit. However, whether the maximum observed lifespan can and has increased is still controversial. According to some scientists, it has remained constant 49 50. In contrast, others have shown that the maximum age at death has been rising over the past century in industrialized countries 51. For ex. statistical analysis of the longest available series of reliable information on the upper limits of achieved human life span, has shown that from 1969 to 1999 maximum life span increased by 1.1 years every decade. The table below shows more specifically the progressive changes in the average and maximum life spans 40.

Average change (in Years Per Decade) in average and maximum life spans in Sweden 51.



Average life span (life expectancy

at birth)



Maximum observed life span (maximum reported age at death)



Thus, even though the average life span has increased more than the maximum observed life span, the data clearly shows that the maximum observed life span is not immutable, and that our life span limit is steadily increasing as well.

Predictors of Successful Aging – valuable lessons from our current centenarians

Let’s take a look at what our current successful elders are doing to age successfully, and what physiological characteristics they display. Centenarians, those who are 100 years old or older, represent an intriguing model for ageing studies, since they demonstrate extreme longevity, and at the same time a proportion of them have aged successfully and have less diseases than the younger elderly 52 53.

It has been shown that autonomous centenarians partake in regular exercise (in proportion to their physical capabilities), have more frequent intakes of protein and regular sleep patterns, and no history of drinking 54.  Other consistent predictors of healthy aging are low blood pressure, low serum glucose, not smoking cigarettes, and not being obese 55. Typical of autonomous centenarians are better visual acuity, preserved masticatory ability and living at home 54. They have been relatively healthy and independent for most of their lives and don’t experience a significant functional decline until the very end of their lives 56.

Other factors that have been documented in centenarians are a higher resting metabolic rate and lower waist-to-hip ratio 57 58, higher IGF-1 levels 59, and preserved thyroid function 60, immunity 61 insulin sensitivity and glucose action 62. Centenarians also have been shown to have a less atherogenic plasma lipid profile (lower LDL and higher HDL, and larger LDL and HDL particle sizes) than aged subjects 63 64. Also, while the prevalence of dementia increases with age, it is not inevitable in centenarians 65-67, and cognition actually seems to be important for longevity 68.

The rise of Generation C

According to watchers of consumer trends, a new generation – Generation C – will emerge in the course of the next 10 years. Born after 1990, they are referred to as “digital natives”. Now beginning to attend university and enter the workforce, they are expected to transform the world as we know it 69. The “C” stands for “connected,” “communicating,” “content-centric,” “creative,” and “change”; however, it may just as well stand for “centenarian” as for the first time in history many of this birth cohort will live 100 years or more.

Centenarians, once considered rare, are now starting to become commonplace. Indeed, they are the fastest growing demographic group of the world’s population, their numbers having roughly doubled every decade since 1950, and they are globally projected to more than quintuple between 2005 and 2030 70.

Allostatic load – small insults add up over lifetime

Beyond the biological effects of aging, much of the illness and disability in the elderly is related to risk factors present at younger ages 55. If you are in your 30s and think “I start to worry about that when I hit 50” you’re wrong. The sooner you start to take care of your health by exercising regularly and eating healthy, the better off you will be when you get older. Even early age nutrition and exercise habits in kids and teenagers have an impact the aging process 71. It has been shown that healthy lifestyle choices encompassing diet, physical activity, body fat (weight) reduction and stress control can add at least ten years to healthy, good quality, life expectancy 72.

Related to successful aging and the risk for diseases and functional declines is allostatic load, which is the cumulative physiologic toll “wear and tear” exacted on the body over time by efforts to adapt to life experiences and demands 73 74. Allostatic load is measured through a composite index of indicators of cumulative strain on several organs and tissues, but especially on the cardiovascular system, and reflects the damaging consequences of the body’s response to chronic stress 75 76.

Higher allostatic load scores have been associated with increased mortality 73 and poorer cognitive and physical functioning 74, and predict larger decrements in cognitive and physical functioning in older men and women  74. In addition to being an index of wear and tear on the body, elevations in allostatic load predict an increased risk for the incidence of cardiovascular disease, independent of sociodemographic and other health risk factors 74. Allostatic load is also an independent predictor of functional decline in elderly men and women 77.

Thus, even if you’re in your 20s or 30s, it is smart to think about the health implications of your current habits and lifestyle.

It is never too late

If you think after having read the previous paragraph “Shoot, it’s too late for me now, the damage is already done”, you’re wrong! Several studies have shown that improving health related habits and reducing risk factors even at older ages confer substantial benefits.

For example, a study followed middle-aged men (45-68 years) who were free of morbidity and functional impairments at baseline, over to 40 years (1965-2005). The purpose was to assess overall and exceptional survival. Exceptional survival was defined as survival to 75, 80, 85, or 90 years without incidence of 6 major chronic diseases and without physical and cognitive impairment. Of the participants, 42% survived to age 85 years and 11% met the criteria for exceptional survival to age 85 years. High grip strength and avoidance of overweight, hyperglycemia, hypertension, smoking, and excessive alcohol consumption were associated with both overall and exceptional survival. In addition, high education and avoidance of hypertriglyceridemia were associated with exceptional survival, and lack of a marital partner was associated with mortality before age 85 years. A statistical risk factor models indicated that the probability of survival to oldest age is as high as 69% with no risk factors and as low as 22% with 6 or more risk factors. The probability of exceptional survival to age 85 years was 55% with no risk factors but decreased to 9% with 6 or more risk factors. Thus, if you have any of the common risk factors that face most middle-age individuals, and make lifestyle changes to correct them, you will increase your probability of a long and healthy life 78.

In another study that evaluated the relationship between changes in physical fitness and risk of mortality in men, it was found that going from being unfit to fit leased to a reduction in mortality risk of 44% relative to those who remained unfit 5 years later, even after adjusting for other risk factors. For each minute increase in maximal treadmill time, there was a corresponding 8% decrease in risk of mortality. This is quite impressive, and should encourage unfit folks to improve their fitness by starting a physical activity program even if they are in the middle-age 79.

In a study of the impact of middle-age physical activity on physical function in early old age, individuals aged 39 to 63 years at baseline, were followed to 9 years. It was found that relatively fit and healthy middle-aged men and women who were physically active at recommended levels, were more likely to report high physical function at follow-up, compared to their sedentary counterparts. The association between initial level of physical activity and high physical function at follow-up remained after adjustment for baseline level of physical function and the presence of long-standing illness. Thus, participation in a physically active lifestyle during mid-life appears to be critical to the maintenance of high physical function in old age 80.

Benefits of risk factor prevention in Americans aged 51 years and older was shown in a study that assessed the potential health and economic impact of reducing common risk factors in older Americans. The gain in life span from successful treatment of obesity, hypertension (high blood pressure) and diabetes was estimated to be up to 4 years. Despite living longer, those successfully treated for any of these risk factors would have lower lifetime medical spending, which indicates that the extra years added to life are healthy disease free years 81.

Even at old age we have a notable capacity to adapt to regular exercise. Aerobic exercise results in improvements in functional capacity and reduced risk of developing type II diabetes in the elderly. High-intensity resistance training (above 60% of the 1 repetition maximum) has been demonstrated to cause large increases in strength in the elderly. In addition, resistance training results in significant increases in muscle size in elderly men and women, and has a positive effect on multiple risk factors for osteoporotic fractures in previously sedentary post-menopausal women. Thus, old age does not decrease the capacity to adapt to a progressive resistance training program, and exercise may minimize or reverse the syndrome of physical frailty which is so prevalent among the oldest old 82. Even in very elderly 87 year old people resistance exercise training is a feasible and effective means of counteracting muscle weakness and physical frailty 83.

A very interesting study sought to characterize the muscle weakness of the very old and its reversibility through strength training 84. Ten frail, institutionalized volunteers aged 90-96 years undertook 8 weeks of high-intensity resistance training. Strength gains averaged 174% and midthigh muscle area increased 9.0%, while gait speed improved 48% after training. It was concluded that high-resistance weight training leads to significant gains in muscle strength, size, and functional mobility among frail residents of nursing homes up to 96 years of age 84. Thus, with exercise training of sufficient frequency, intensity and duration, it is quite possible to increase muscle mass, strength and endurance at any age, and prevent sarcopenia, obesity, type II diabetes, coronary artery disease, hypertension, and osteoporosis. There is no pharmacological intervention that holds a greater promise of improving health and promoting independence in the elderly than does exercise 85.

These studies clearly prove that it is never too late to start living healthier and benefit from those changes. While it’s certainly better to start healthy habits at a young age and keep them for a lifetime, for those who have strayed (that is, most people!) nature is remarkably forgiving. Not only can we recover much lost function and decrease risk, but we can actually increase function and health beyond our prior level.

The three steps toward extending your life and health span

One way to look at our path to longevity and health span is to regard it as a journey over three sequential steps. Step 1 is based on therapies that exist today, like exercise, nutrition and dietary supplementation. Step 1 will take us to step 2, which consists of biotechnology therapies. Step 2 will then take us to step 3, the nanotechnology/artificial intelligence revolution, which will lead to life spans that are currently incomprehensible, but which will soon be commonplace, measuring in the hundreds of years 86 87.

The step 2 and step 3 anti-aging technologies, which have potential to extend our health span more than we ever dreamed was possible, are controversial topics and surrounded by ethical and political issues. Since BrinkZone is a site about nutrition and exercise, I will not cover these topics here.

Wrap up

There’s no excuse to treat the aging process itself as a reason for disability and disease at older age. A wealth of studies are showing over and over again that many, if not most, of the aging related functional declines and disabilities and can be prevented with non-aging related lifestyle factors like exercise and nutrition. A successful old age lies not so much in out stars and genes, as in ourselves. Step up, take control, and start adding both years to your life, and life to your years!

In part two of this article I will cover nutrition and dietary supplements that are currently being researched for their potential anti-aging effects, and that you can expect to see popping up on the supplement shelves in the near future. Stay tuned!


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About Monica Mollica > www.trainergize.com

Monica Mollica has a Bachelor’s and Master’s degree in Nutrition from the University of Stockholm, Sweden, and is an ISSA Certified Personal Trainer. She works a dietary consultant, health journalist and writer for www.BrinkZone.com, and is also a web designer and videographer.

Monica has admired and been fascinated by muscular and sculptured strong athletic bodies since childhood, and discovered bodybuilding as an early teenager. Realizing the importance of nutrition for maximal results in the gym, she went for a major in Nutrition at the University.

During her years at the University she was a regular contributor to the Swedish bodybuilding magazine BODY, and she has published the book (in Swedish) “Functional Foods for Health and Energy Balance”, and authored several book chapters in Swedish publications.

It was her insatiable thirst for knowledge and scientific research in the area of bodybuilding and health that brought her to the US. She has completed one semester at the PhD-program “Exercise, Nutrition and Preventive Health” at Baylor University Texas, at the department of Health Human Performance and Recreation, and worked as an ISSA certified personal trainer. Today, Monica is sharing her solid experience by doing dietary consultations and writing about topics related to bodybuilding, fitness, health and anti-aging.




Monica Mollica holds a Master Degree in Nutrition from the University of Stockholm and Karolinska Institue, Sweden. She has also done PhD level course work at renowned Baylor University, TX.


Monica is a medical writer, diet/supplement/health counselor and body transformation coach, and a regular contributor to www.BrinkZone.com.


Check out Monica's website:        www.Ageless.Fitness


She can be contacted via email:   Monica@Ageless.Fitness


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