A long-term study found a connection between higher BMI during adolescence and faster biological aging later in life.
Researchers followed thousands of people for decades and used genetic data and DNA-based measures to study the relationship.
The findings suggest that higher BMI during the teen years may contribute to faster biological aging, although the researchers say more work is needed.
Getting older on the calendar and aging biologically aren't necessarily the same thing. While chronological age simply counts the years someone has been alive, biological aging looks at how quickly the body appears to be aging based on changes happening at the cellular level.
A new study published in the International Journal of Obesity suggests that having a higher body mass index (BMI) during adolescence may be associated with faster biological aging later in life.
The researchers were particularly interested in whether genetics and weight during the teenage years could help explain differences in how quickly people biologically age. The study doesn't mean that a person's BMI determines exactly how quickly they will age, but it adds to research looking at how weight earlier in life may be connected to health decades later.
“Our findings suggest that genetic predisposition to high body mass index is associated with accelerated biological aging,” Doctoral Researcher Anni Pitkänen said in a news release. “Part of this association may be explained by the fact that the inherited predisposition is reflected in higher adolescent BMI.”
How did researchers study the connection?
The researchers used information from the Cardiovascular Risk in Young Finns Study, a long-running study that began in 1980. The participants included 3,596 people who were between ages 3 and 18 when the study began, and researchers followed them through 2018–2020.
For the analysis, researchers looked at BMI measurements taken during adolescence, including measurements at ages 9, 12, 15, and 18. They also examined participants' genetic predisposition to having a higher BMI using genetic information involving hundreds of variants associated with body weight.
To estimate biological aging, researchers analyzed DNA methylation from blood samples. They used two "epigenetic clocks" — computer-based tools that estimate biological aging based on changes to DNA. The researchers also used a statistical technique called Mendelian randomization to examine whether genetically predicted BMI might have a causal relationship with biological aging.
What did the study find?
The researchers found that a higher BMI during adolescence was associated with faster biological aging in adulthood. Higher genetic predisposition to BMI was also associated with accelerated biological aging, and some of that relationship appeared to be explained by having a higher BMI during adolescence.
The evidence for a causal relationship was strongest when researchers used the DunedinPACE measure of biological aging. In that analysis, they estimated that a one-unit increase in genetically predicted adolescent BMI was associated with about 0.02 years of faster biological aging per calendar year. However, results were not consistent across all of the biological-aging measures used in the study.
The researchers also noted an important limitation: some of the association may be related to BMI in adulthood, since higher BMI during adolescence can continue into adult life. The study therefore doesn't establish that adolescent BMI alone determines how quickly someone ages.
For consumers, the findings add to evidence that health and weight patterns earlier in life can have long-term implications. But they don't mean an individual teenager's BMI can be used to predict exactly how they will age or what health problems they will develop.
“The results of our study emphasize the importance of preventing overweight and obesity throughout the life course,” Pitkänen said.