Body Fat Percentage
Body fat is the fat that we all keep to use as extra energy. In this post, I would quickly like to fill you guys in on its role in the body, why too much is bad, why having to little is bad, and why it’s the best way to judge overall health with regards to weight.
First, we’ll quickly go over body fat. Adipocytes (aka lipocytes, fat cells) make up the body fat in the human body. They are considered part of the endocrine system as they release the hormone cortisol upon certain conditions. Fat cells store semi-liquid energy in the form of triglycerides and/or cholesterol esters. These are high energy fuel that are very stable in the body and thus easy to store. Fat cells can expand and contract with the addition and subtraction of that fuel. When fuel in the body is plentiful (I.E. we have more fuel than we need at that moment in time) the body will convert and store any extra energy in fat cells. This is a continual process, thus even in a long-term catabolic state (at a calorie deficit) if you flood your body with fuel in the short-term (one meal) you will store fat. This is the reason why bingeing is very bad. This also ties in with simple sugars and carbohydrates. Because of the speed at which those foods are converted to fuel, our body cannot burn them as fast as they are shuttled into the blood, thus we store fat easier with these foods.
Adipocytes are inert tissue. This means they don’t contribute to the metabolic rate in any real sense, they require very little energy to maintain their existence, unlike lean tissue which requires about 6 to 10 times the amount of energy per volume and organs which can take many times that of lean tissue. This being the case, body fat is usually considered a storage mechanism only. Let’s take a look at problems that can arise from excess body fat. When we have excess body fat, our body tends to cluster this fat instead of layering it throughout the body. When there is a large cluster of fat, the muscle structure that supports this area can become stressed, this can lead to muscle deformation and unbalance. Weight from excess fat can also cause structural stress on join and ligament issues over time, forcing your body to warp in order to center balance around the weight (such as a spinal deformation due to excess stomach fat stores). A more immediately dangerous situation can arise when fat is stored on or around organs or arteries (visceral fat) which can squeeze them and increase blood pressure and/or force the heart to work harder to deliver nutrients and oxygen to the body. Lastly as an indirect negative result, generally people with excess fat usually develop insulin resistance because of the continuous increased blood sugar levels (not a direct result of body fat, but usually goes hand in hand).
Now lets see what having to little body fat can do. Granted, most of us don’t have this issue. But being very low in body fat can be just as damaging as being very high. Low body fat means you obviously aren’t eating enough food to store any fat. This is dangerous not only because you have no “buffer” but also because body fat can be used as a storage mechanism not just for fuel, but also for certain vitamins and minerals. “Fat soluble” vitamins can be stored and used as needed, without the fat to store them and transport them, you can become very sick.
All this being said, I like to use body fat to measure the overall health of a person. I don’t mean to say that body fat is the only tool you should use, but generally speaking, someone with healthy body fat levels is indicative of someone who exercises regularly and eats generally healthy. While there are outliers to this theory, it’s relatively rare for someone to be metabolically unhealthy while having a body fat percentage in the accepted ranges of normal.
To test for body fat, there are many different methods. The gold standard is MRI or DEXA testing, although these methods are expensive and not widely offered, they provide the lowest possible margin for error. Next down is the BodPod (air displacement) or hydrostatic (water displacement) methods. These usually offer a very low margin for error at a more reasonable price. After that you have caliper tests, which are less accurate than the above methods but can be quick and cheap, and accurate enough for most people if done by an experienced trained professional (don’t “self test” with calipers, you’ll inevitably be very inaccurate). Lastly there’s bio-electrical impedance testing. While this test can be accurate if done in very controlled conditions, because they test the resistance of fat in the body to electrical impulse, and because resistance changes in water, it’s extremely difficult to receive an accurate reading unless you can confirm and keep hydration levels constant (which is almost impossible at home, and difficult in a lab) thus you normally receive very inaccurate results (worse for those home scale models).
I won’t go into what “good” percentages are for people as there are a plethora of resources out there for that online, but I will say that it’s far different for men than for women (about 10% lower on average for men). Please note that all the things I talk about here are for fully grown adults, children require completely different strategies.