Some people say that age is just a number–what really matters is how old you feel on the inside.

But according to TCM, age is actually pretty important. There’s an ancient Chinese text called the Huang Di Nei Jing, and it lays out the stages of life for both men and women. And all of these stages correspond to certain ages. So cute phrases aside, age really does matter when it comes to your health and TCM.

Here are the basic stages of life for men and women, according to TCM.

TCM Life Stages

In TCM, how you age is based on your biological sex. For women, who are thought to have strong yin energy, their lives are divided up into 7 stages. That’s because 7 is an odd number, so it’s associated with yang energy. Why the opposites? If you’ve ever seen a yin-yang symbol, you know that yin has a little bit of yang in it, and yang has a little bit of yin in it. That’s the idea behind this.

Here are the 7 life stages for women:

1. The first change in a girl happens when she’s 7 years old. At this time, her Kidney energy starts to become stronger. She starts to grow more, and her hair and teeth change.
2. At 14, girls tend to start their periods. According to TCM, this is because the Ren meridian opens up and both blood and Qi start to flow through the Chong meridian.
3. When she’s 21, a woman’s Qi becomes balanced, she’s grown as tall as she will, and her teeth are done growing.
4. In TCM, 28 is considered the physical peak of a woman’s life. If you’re healthy, your Qi and blood should be plentiful and powerful.
5. After 28, your body starts to decline slowly. Starting at 35, your yang levels start to go down. You might notice some new wrinkles and your fertility is decreasing.
6. At 42, your yang takes another big hit. You might not have as much energy as you used to.
7. By 49, your Ren and Chong meridians have become weak, so you’ll experience menopause.

For men, things are a little bit different. Because men are thought to have yang energy, their life stages go in groups of 8 years (an even, therefore yin, number). Here’s the 8 stages:

1. By the age of 8, a boy has strong Kidney energy (this organ is the driving force behind all growth and energy in the body), and his teeth and hair are growing.
2. By the time he’s 16, a young man’s Kidney is still growing, giving him plenty of energy and vitality.
3. The Kidney reaches full development by the time a man is 24, so he’s approaching his peak physical condition. He should be strong and healthy, with his teeth fully developed.
4. At 32, a man’s body is supposed to be as strong and healthy as it will be.
5. But by the age of 40, your Kidney starts to get weaker. That means you7r hair may fall out and your teeth become more sensitive.
6. The older you get, the weaker your Kidneys become. So by 48, most men are showing visible signs of age, including graying hair or balding.
7. By 56, your Liver is starting to decline alongside your Kidney. Your muscles will get weaker and you’ll feel less flexible.
8. At 64, your body’s vital energy is low, so you really start to feel the effects of aging. You might lose teeth and hair while feeling frail.

What’s the takeaway from all this?

Well, basically everyone has two forms of life essence–the kind we inherit from our parents (called Jing) and the kind we get from things like food, medicine, and sleep. When we’re kids, this essence is on an upward trajectory. We’re getting stronger, growing, and heading toward full maturity. But after a certain point, that energy we inherit from our parents starts to decline. We can still get energy from food, but overall, our life force capacity decreases bit by bit. 

And after 35, this decline becomes faster. That’s why you might notice some changes in your body as you get older. 

Why Things Change As We Age

Whether you’re 30 or 60, you’ve probably noticed some changes in your body as you age. You’ve racked up a few wrinkles, you get a monster hangover after just a few drinks, and your neck hurts for weeks after you sleep in a funky position. 

Here’s why our bodies change as we get older, according to TCM.

Our Metabolism Slows Down

Your metabolism is responsible for taking the energy and nutrients from your food and turning it into something your body can use. Our jing essence (which comes from the Kidneys) is a major driving force in this process. But alongside your Kidney, the Stomach and Spleen are also important for your metabolism. They need plenty of life energy, or Qi, to function the best they can.

What this all means is that to have a powerful, fast metabolism, you need powerful Jing essence and strong Qi. As we get older, both of these things decrease naturally, which lowers our metabolism.

But all hope is not lost! You can boost your metabolism by staying active, maintaining muscle mass, eating lots of protein, and getting plenty of sleep.

We Can’t Drink As Much

Do you ever find yourself saying, “I just can’t drink and party as much as I used to.” Sure, hangovers get worse the older we get. But our body also starts to be slower at breaking down the alcohol we drink. That means it stays in our system longer, so our tolerance seems to go down. You might have been able to polish off half a bottle of wine in your 30s, but can’t quite handle the same amount when you’re 60.

But it’s not just about metabolizing the alcohol. Other parts of your body are becoming weaker as you age, like your eyesight, hearing, and balance. That means your reflexes and senses become even duller when you drink, so you’re more likely to fall or get in an accident when you drink.

From the TCM point of view, alcohol is a warming drink. It can stimulate your blood and your Qi in small amounts. But when you overdo it, it can throw your body’s balance out of whack. So the older you get, the less alcohol it takes to mess with your balance. Your Jing essence is weaker and you can’t filter out the toxins in your blood as well, thanks to your aging Kidneys. So both western and eastern medicine agree, as you get older, less is more when it comes to alcohol.

Aging is a natural process, and you can’t ever stop it completely. But knowing how and why your body changes as you get older can give you the power to stay healthy, happy, and energetic at any age.