On a cellular level, how does exercise make us healthy or improve our health?
In: Biology
Ancient humans had to hunt or gather food to get energy. At the same time, ancient humans used a lot of energy (compared to other animals): Humans hunted by tracking and tiring other animals out. Human babies spend a lot of their life burning energy and not collecting energy. Human brains burn a lot of energy. Humans need a lot of energy.
Thus, human bodies evolved to be very efficient: 1) Store extra energy as fat to not waste it 2) Only grow muscles that are used in order to conserve protein and energy.
But human society suddenly changed human behavior: We could get energy by just buying food. Because we could just buy food, we ate excess energy, which we store as fat. Because we could just buy food, we didn’t have to use as many muscles to gather food so we stopped building muscles.
Why is excess fat bad? Fats produce hormones. Hormones are signals or messages to the body about the state of the body. Hormones mostly signal based the *amount* of the hormone in the body. Too much fat, too much of fat’s hormones, and the body starts misbehaving. Fat also releases cytokines, which are not exactly hormones, but too many cytokines seem to constantly activate the immune system, which makes the immune system unable to respond to actual attacks.
Why is too little muscle bad? Well muscles help us move, help support us, and help prevent us from getting injured. Too little muscle and we get injured easily, can’t move well, and can’t support our own weight (and we get things like lower back pain and bad posture.) Muscle mass also tends to calm the immune system. And the other important muscle is the heart! If the heart isn’t challenged, it doesn’t get stronger and is less resilient, ~~and it pumps less blood per pump, which can contribute to high blood pressure.~~
TL;DR: Because energy was scarce, we evolved to store energy as fat and to only grow muscles when needed. When energy became abundant and easy to gather, we gained too much fat and lost too much muscle. Too much fat unbalanced the body and too little muscle leads to not being able to move well and more likely to get injured.
Cardio exercise is an attempt to reduce fat (though you can also eat less) and to strengthen the heart and breathing muscles. Resistance exercise (moving heavy objects) is an attempt to fool muscles into thinking they are needed, so the body will spend energy growing and maintaining those muscles.
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