Body Fat Facts 101 - The Fat Cell

Thomas Richardson

Body Fat Facts 101 Part 1

Well since most of us want to lose this thing we call fat, we should know a little about it, and there is a lot to know some of which science is still learning. So, what is body fat? Body fat or adipose tissue as science calls it, are cells containing a substance called triglycerides, which is a combination of glycerol and fatty acids. Simply, fat cells are storage units for energy, in the form of triglycerides.   We have two main types of fat subcutaneous and visceral.   Subcutaneous fat is that fat you can pinch on your stomach, it’s the fat right under the skin.  Visceral fat is under the muscle and surrounds your organs.  Visceral fat is considered toxic and spells double-trouble in the body because it’s capable of provoking inflammatory pathways, plus signaling molecules that can interfere with the body’s normal hormonal functions. In fact, it acts almost like its very own organ since it’s capable of having such a large impact on the body.

There is a third type of fat cell, that is the brown fat(the good one). Brown fat cells, unlike white, generate heat to keep us warm. The main difference between white and brown fat lies in their color and namesake. Inside a white fat cell sits a single large lipid (fat) droplet and not much else. That fatty deposit gives the cell its color and claim to fame, storing energy and providing a nice cushion for our internal organs. It also produces a whole bunch of hormones, like estrogen and leptin (which regulates hunger), and contain receptors for others like insulin.


But the composition of a brown fat cell is completely different. Instead of one huge fat chunk, it contains a handful of tiny fat droplets and a huge number of mitochondria. Those cellular powerhouses contain iron—giving them a brownish color, hence the name—which fuels them to burn away the tiny fat droplets. Yes, you have fat cells that burn the fat you eat. Brown adipose tissue (BAT), in contrast to bona fide white fat, can dissipate significant amounts of chemical energy through uncoupled respiration and heat production (thermogenesis). I will tell you stimulating brown fat is a good thing.  The other interesting fact is that white fat can be converted to brown.  More on that later

Fat Fact: a pound of fat is 454 grams; a gram of fat is 9 calories so each pound of fat is about 3500-3600 calories.  It’s not exact because fat does contain some water and a few other things not of importance at this time.

So why do we have fat and what does it do?

Well to start this discussion we need to go back and present a theory that we believe in, and that is the fact that we are here is proof that our genes are survivor genes.  What we mean by that is if our genes were weak our ancestors would have died off long ago and we would not be here. And one of the biggest hurdles our genes have overcome is starvation.  Yep, our genes know how to survive very well without food for extended periods.  Our genes also know what to do when we have available food, and that is eat and eat and store it for when it is gone.  So now you know the main reason why we have fat, to store energy.  Fat is the most calorie dense element we have at 9 calories a gram versus carbohydrates and protein which have 4.  Alcohol by the way has 7 grams, now you can impress your friends next time you are shooting tequila.  

Another reason science believes we have fat is to keep us warm to protect us from the cold weather.  Well, we don’t need that, anymore right?  Additionally, some researchers believe we have visceral fat to protect our organs when we are jumping around hunting for food or fighting off adversaries.  Again, we don’t need that anymore. 

Up until the mid 1990’s it was thought that the fat cell was a dumb repository of energy.  But, science has now determined that couldn’t be farther from the truth, the fat cell is an intelligent hormone producing organ. As of today, it has been determined that the fat cells produce more than 80 hormones and proteins, and new ones are being discovered all the time.  More on these in a later post.

How does the fat cell grow and how does it shrink?

Eat and absorb more calories than you burn, eat and absorb less calories than you burn.  That’s the quick answer.  Easier said than done right, that’s why we are an obese society.   Let’s look at fat cell, and make believe for this point, that it has doors. It has entry doors and exit doors.  As food is digested and enters the blood stream, insulin grabs onto it and transports it to our muscles and liver and when those are full, it transports it to the fat cell for storage.  It is so much more complicated than that but for this post, insulin opens the fat entry doors and dumps in fat. At the same time insulin tells the exit doors not to open, reason is why would you empty your energy reserves when you have food in your system. Because insulin is released when you eat. Now let’s flip it around, you are burning more calories than are available in your blood stream, could be that you have not eaten in a while, and/or could be you are exercising whatever it is, you are in a caloric deficit.  What happens is that the body turns to the most readily fuel source available, glucose, which insulin has stored in the liver and muscles.  We don’t store a lot of glucose compared to fat, so glucose stores run out quickly. At this time your body tells your fat cells to release fat, how it does this is part of another post.  Insulin at this point is low so the exit doors can be opened and fat is released as fatty acids into the bloodstream to be used as energy.  The term for release fat from the cells is called lipolysis, and the term for fat burning is oxidation.  We want both those things to happen in order to lose fat.

Those are  the basics, but at least you have some perspective of function.


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