If our body is trying to conserve energy by losing muscle mass we’re not using, why does being sedentary ultimately end up being more harmful?
In: Biology
Humans evolved in an environment where conserving energy was a definite survival advantage as food availability wasn’t guaranteed – so the human body developed a ‘use it or lose it’ system.
But humans also evolved in an environment where survival involved constant physical activity whether that was hunting, searching, foraging, fleeing, etc.
So the ‘use it or lose it’ system never needed to develop a safety net, because humans tended to maintain a minimum level of physical activity, especially when food was scarce.
So these days, the ‘use it or lose it’ still functions, except people don’t tend to starve if they’re not active. So the musculoskeletal system – bones, tendons, ligaments, joints and muscles – will slowly degrade to the point where your skeleton will struggle to just support your own weight.
The cardiovascular system and your aerobic capacity undergo similar atrophy, and there’s also the fact that people who live sedentary lifestyles rarely tend to adjust their calorie intake accordingly which leads to weight gain that exacerbates all the other issues.
I’m no expert (at biology, you better believe i’m one hell of a sedentariologist)
But it has more to do with cardiovascular health than musculature (also like every other part of the body is affected of course) being sedentary means you aren’t getting cardiovascular exercise, which as running and wandering organisms is *very* important to the normal fuctions of a homosapien. Poor cardiovascular health means your body is less efficient at spreading oxygen and other nutrients to your cells. Poor nutrition amd oxygenation of cells means they work harder and are more prone to errors or failure. Poor cardiovascular health is the #1 killer in the US, and creates more problems than I could list here.
It is more energy taxing for the body to maintain lean muscle than it is to hold fat. If the muscle tissue isnt consistently stimulated in order to promote maintenance or building of lean tissue, the body wont waste calories to do so. Holding adipose (fat) tissue allows the body simpler and less energy intensive stores of energy for use in case of a lack of calories.
Therefore sarcopenia (loss of muscle tissue) occurs as one ages and is sedentary, and the rate of sarcopenia increases as we age due to hormonal changes that occur naturally.
So we conserve energy by eliminating lean tissue and we will happily store excess energy as adipose fat. Adipose Fat storage and Low Lean mass had been directly correlated to all cause mortality and a slew of secondary diseases such as Hypertension, Diabetes, etc
When we think of how humans are in every way we need to realize that we were a tribal species for like… a million years. Actually we were tribal before we were even human. Every thought, action, desire, and manner of our mind and physiology is refined and perfected for tribal life. How we live now is nothing like the life we evolved for, which makes our lives confusing in modern times. For most of human history humans had replicated themselves a bunch of cubs and died before the age of 40. Think about this for a sec. Most chronic diseases, cardio vascular disease, diabetes, cancer, neurological, autoimmune, etc, and other health ailments, occur after the age of 35. With means there was no evolutionary selection pressure giving us genetic defenses against such diseases past about the age of 40.
So basically in our younger lives we can be sedentary, or not, and it won’t really affect our health is such a way that would prevent us from replicating before the age of 40. All these diseases we try to prevent these days is just us trying to live 2-3 times longer than we ever evolved to.
Being sedentary isn’t particularly harmful if you’re just trying to live the “normal” life nature evolved us for where we die before any of these health ailments would get us. Your question is outside the bounds of evolutionary biology since the reason we live long enough to get these diseases has more to do with technology than fitness evolution.
Because then you get old and are now weak and then life gets hard. Then you get injured more easily and your body can’t recover because it isn’t adapted to that kind of stress (whereas if you exercise it’s like a bunch of mini little stressors to prepare you).
A scenario where you’re losing muscle mass is your body’s response to Improper or not enough energy intake, ie. nutritional food. This is a survival tactic and not beneficial for longterm health.
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