Getting younger: Does chronological age matter when you can wind back the clock on biological age?

As a law change in South Korea means its citizens will become a year or two younger, we explore what measuring age really looks like.

Another orbit round the Sun, another cake on the candle, another year on the clock… we all know about aging – but this, in the longevity biz, it’s what’s known as chronological age.

Chronological age refers to the number of years you’ve lived, how old you are legally, but there is another, perhaps more pertinent, measure of how old you are – biological age. Your biological age refers to the age of your cells and tissues based on physiological evidence.

Your biological age may be lower than your chronological age if you’re quite healthy and fit. In contrast, your biological age may be higher if you are sedentary, chronically ill or in poor physical condition. And genetic, environmental and epigenetic factors have a role to play as well. Oh, and different organs and tissues can have different biological ages as well!

A new system for age in South Korea

In South Korea, the government has passed laws to replace its traditional methods of counting ages with an international standard. This will have the interesting result of many South Koreans becoming younger by a year or two.

Currently, South Koreans have Korean age, which means a person is one at birth and gains a year on each New Year’s Day. This means that a child born on 31st December would be regarded as two years old the following day.

To compute the legal drinking and smoking age, a different method is used. The age of a person is calculated from zero at birth, and one year is added on 1st January.

In addition to this, South Korea also uses the international method to calculate age, starting at zero at birth and adding one year for each birthday afterward. To clarify any confusion, the country will officially adopt the international standard from 23rd June next year – at least on official documents [1].

The move aims to standardise how age is calculated in the country.

Yoo Sang-bum, of the ruling People Power Party, told parliament: “The revision is aimed at reducing unnecessary socio-economic costs, because legal and social disputes as well as confusion persist due to the different ways of calculating age.”

The deal with biological age vs chronological age

In contrast to chronological age, biological age refers to epigenetic alteration and DNA methylation, which indicate the capability and functioning of an individual and whether or not they are susceptible to diseases associated with old age [2]. 

There is evidence to back up the conclusion that biological age is a more accurate predictor of disease onset and death than chronological age [3]. In terms of longevity, we could work with “winding back” our biological clock by making lifestyle changes.

What determines biological age?

Your biological age can be lowered in a variety of ways. In general, they’re the exact options you’ve heard about for staying healthy:


In a 2018 study on nutrition and biological age, it was found that eating a high-nutrient diet can reduce your biological age [4]. Nutrition data was examined as a factor in people’s food selection decisions. 

The more attention paid, the lower the biological age. There was a greater difference among those who:

  • Are chronically ill
  • Are obese
  • Are older
  • Have a family background of chronic disease
  • Have a lower education level

When it came to choosing foods, they also found a sex-based difference: just under 13 percent of males thought about nutrition data, compared to 27.5% of females. Other studies on diet and biological age suggest the ideal diet is:

  • A Mediterranean diet
  • High in fish
  • Low in calories
  • Plant-based


According to research on biological aging, higher activity levels correlate with a younger biological age [5]. Increased exercise does not affect biological age in all studies. However, a growing body of research supports the idea that it does:

  • Several biomarkers of aging and disease, including cancer, slowed down in post-menopausal women in 2021 [6].
  • In 2022, a study found that changing your diet and increasing your exercise reduces your biological age more than either dietary changes alone or increasing exercise alone [7].
  • Researchers found that aerobic exercisers were almost 5.5 years younger than sedentary people in a study published in 2020 [8].

The physical environment

Where you live, work, and spend most of your time is your physical surroundings. Environmental factors determine how much air pollution and other pollutants or harmful materials you’re subjected to.

Your biological aging can be accelerated by those toxins but taking steps to reduce your exposure is one way to avoid it. This may be able to reverse the effects, according to research.

Nevertheless, some of these hazards may be challenging to eliminate. The good news is that other healthy changes, such as sleeping more or better, can reverse pollution-induced aging [9].

Sleeping habits

In addition to affecting your health and longevity, poor sleep also increases your biological age. It is recommended that adults get seven hours of sleep each night [10]. 

The majority of people, however, do not. Lifestyle factors or sleep disorders may be responsible for this. Your health also depends on the quality of your sleep.

Researchers have found that if you sleep more and better, you can reverse biological aging. Make simple changes to improve your sleep, like going to bed earlier, turning off screens before bed or reducing distractions.


There is evidence that physical and psychological stress can reverse biological aging. Researchers in 2022 examined the effects of stressors such as [11]:

  • Pregnancy
  • COVID-19 infection
  • Trauma
  • Surgery

By measuring DNA methylation, they found that biological age increases rapidly during stressful times. After the stressor was removed, it returned to baseline within a few days.

Researchers found that individuals who are emotionally resilient and can regulate their emotions can avoid the aging effects of psychological stress in a 2021 study [12].

Speak to a healthcare provider if you have significant physical or psychological stressors. An appointment with a mental health professional may be beneficial to you.

Tobacco use

There is no doubt that smoking causes serious health problems and shortens your life. Smoking increases your biological age [13].

The effects of smoking on aging, however, appear to be somewhat reversible, as is the case with stress. In studies comparing current smokers, former smokers and non-smokers, researchers found that former smokers have the same biological age as non-smokers. But really, it’s better to have never smoked at all.

Time to make a change

Your chronological age indicates how long you’ve lived. A person’s biological age determines how long they have left and the likelihood that they will become chronically ill.

A professional medical test for telomere length and biomarkers of DNA methylation is needed to determine your biological age, but these are increasingly becoming more available, although commercial tests and online calculators that claim to measure biological age may need validation.

A person’s biological age can be changed, unlike their chronological age; as with so many things in longevity, changing your habits can make a big difference, and making wise lifestyle choices with regard to dietary habits, exercise, stress levels, sleep quality and smoking can make all the difference. South Korea may be passing a law to change its citizens’ ages, but when it comes to biological ages, it’s all down to the individual.