Elena Scotti/FUSION

I got my period when I was 15-and-a-half years old, much later than most of the girls I knew. This meant that, until well into my teens, while my classmates were chatting about pads, tampons (gasp!), and dating, I was off studying, as I had nothing to say on those subjects.

Little did I know at the time that my¬†late entrance into "womanhood" may have worked to my advantage, both physically and mentally. I¬†may not have gotten any male attention in high school (it's true, no one asked me to prom ūüė≠), but I did get into some pretty sweet colleges.

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From academic success to cancer risk, research increasingly shows that the age at which a girl gets her period‚ÄĒcalled "menarche"‚ÄĒcan have a significant¬†impact on her¬†life.

These findings are especially notable¬†given that, around the world, the average age of menarche has dropped steadily since the 1950s. With new studies coming out regularly¬†about girls going through puberty earlier, we were curious:¬†What's causing this global decline‚ÄĒand what¬†are the potential long-term consequences?

Not girls, not yet women

It turns out that if I had been born in the 1800s, I would have been on the early side for getting my period. In the mid-19th Century, the average age of menarche in the U.S. was around 17 years old (though given that slavery wasn't outlawed until 1865, that data was not likely entirely representative). By 2002, it had dropped to 12.6 years old, according to the CDC, and by 2010, to 12.5 years old.

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And it‚Äôs not just an American trend. This decline has been seen from first-world to third-world countries‚ÄĒsimilar stats are reflected¬†from France¬†to India‚ÄĒand across races. (In the U.S., black and Latino girls are most likely to get their period early. The¬†average¬†menarchal age¬†for black women in this country is 12.1 years.)

So what explains the decline? While researchers¬†have a few different theories‚ÄĒincluding exposure to¬†chemicals¬†in the environment or food that affect our hormones‚ÄĒexperts believe¬†the biggest and most basic culprit is an increase in fat in our¬†diets.

The average age of menarche in the mid-19th¬†century was higher because girls were often undernourished. Lower body fat meant puberty was delayed‚ÄĒthe body's way of saying it wasn't prepared to carry a child yet. This all changed in the 20th¬†century.

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As more fat was introduced¬†into girls‚Äô diet, the body responded by initiating puberty earlier‚ÄĒand "that wasn't necessarily an unhealthy thing," said Julianna Deardorff, an associate professor in the Maternal and Child Health Program at UC Berkeley and coauthor of the book¬†The New Puberty: How to Navigate Early Development in Today‚Äôs Girls.

But during the 1950s and 1960s, this country saw a tipping point. Nutritional needs had been met, but the introduction of processed foods, microwaves, and other changes in America's eating habits caused the age to keep dropping. That's when the trend became unhealthy.

No longer were girls getting their period earlier because the right amount of fat had been introduced‚ÄĒnow they were getting their periods sooner because they were¬†getting too much fat.

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Why does fat matter so much?

Experts don’t know exactly what triggers puberty, but they believe fat plays a major role.

"Puberty takes a great deal of energy‚ÄĒyour body is accelerating‚ÄĒand if¬†you don't have enough energy, you're not going to go into puberty," said¬†Frank Biro, the director of research for the Division of Adolescent and Transition Medicine at Cincinnati Children's Hospital Medical Center. "A larger BMI is associated with a higher level of the hormone leptin, which tells the body you have enough energy reserves to engage in this pursuit called puberty."

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Thus, women¬†with extremely high BMIs for their age may start puberty as young as 7 years old, and in turn, get their period before age 11‚ÄĒincreasing their risk for a host of psychological, social, and health issues (more on these in a second).

The obesity trigger may also explain why girls raised in lower income families, many of whom are black and Latino, face the highest risk for early menarche. As Deardorff told me, "African American and Hispanic kids are often inside a lot because it’s just not safe to go outside. They have less access to places to be active. Their parents are working, maybe one or two jobs, and putting healthy food on the table is difficult."

Which also makes this very much a socioeconomic problem.¬†It‚Äôs been well-documented¬†that many lower income families don't have access to or can't afford fresh food, instead opting for what's cheap‚ÄĒlike soda and processed foods. (In fact,¬†two studies¬†recently linked soda intake¬†with early age of menarche).¬†And this processed food trend isn't just happening in America.¬†Around the world,¬†kids are being exposed to more fattening, less nutrient-dense foods,¬†according to the World Health Organization.

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But beyond the obvious perils of ingesting too much fat, what's the lasting impact of earlier menarche?

Period age can impact your mental health

Going through puberty before age 11 has been linked to a host of psychological and social challenges‚ÄĒfrom depression to eating disorders to all the problems that come from being viewed as a sex object while still a little girl.

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For many, early menarche can mean being forced to grow up before¬†one's¬†mind, and¬†decision-making abilities,¬†are ready.¬†"If¬†you‚Äôre 11 and you look like you're 15 or 16, people will treat you like you‚Äôre 15 or 16," Biro said. Just because you're¬†physically going through these changes, he added, "it doesn't mean your brain is going through these changes.‚ÄĚ

While it's tricky to nail down the root causes, research has shown that, as a group, women who go through menarche early also achieve lower levels of education (compared to women who go through puberty later), and exhibit more high-risk social behaviors such as smoking, drinking, using drugs, and having unprotected sex, which can bring on its own set of problems. They also tend to draw older peers to them and have older boyfriends. As a result of all these factors, they often struggle with self-esteem and anxiety, Deardorff told me.

These trends suggest that what happens to a girl's body at age 7‚ÄĒthanks to circumstances¬†beyond her control‚ÄĒcould affect her for the rest of her life.

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Period age can impact your physical health, too

But on top of the psychological and social challenges, getting your period young is associated with a slew of health risks. Notably, research suggests that women go through menarche early are more likely to develop breast cancer, diabetes, and cardiovascular disease. All of these correlations are currently being explored.

The cancer risk may boil down to being exposed to estrogen for a longer period of time, as well as developing breast tissue sooner. A large meta-analysis study published in 2012, which included more than 400,000 women, found that risk of breast cancer increased by 5 percent for each year younger the women reached menarche. "Increasing that window of susceptibility can be a bad thing," said Biro.

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Another study, published in¬†Cancer Epidemiology, Biomarkers & Prevention,¬†found that ovarian cancer patients whose age of first menstrual cycle was younger than 12 were associated with higher mortality rates‚ÄĒthey were 51 percent more likely to die from the cancer than those whose age at menarche was 14 or older.

What can we do?

Stabilizing the age at which girls get their period¬†requires hitting the issue at its source‚ÄĒwhich means combatting unhealthy diets and childhood obesity, an issue with many, many layers.

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In the meantime, adults can look out for the individual girls in their life. "We are are doing a lot of work right now to mitigate" the effects of early menarche," Deardorff told me. "A lot of it resides in the family and in parental monitoring, particularly if a young girl is going through it early."

In other words, when a girl does get her period at a young age, her family can and should step up to help her navigate the social challenges that may lie ahead.

Related: Does your vagina change at 30? Diva Cups says yes.

Taryn Hillin is Fusion's love and sex writer, with a large focus on the science of relationships. She also loves dogs, Bourbon barrel-aged beers and popcorn ‚ÄĒ not necessarily in that order.