Obese individuals tend to have little to no brown fat. Brown fat actually burns calories into heat in a process referred to as thermogenisis. It can also only be detected in body scans when an individual is cold. Intrigued? I’ll get to more about brown fat in a minute.
Have you ever wondered what fat really does and how it interacts with the rest of our body, what it releases? When fat enters our body it is broken down in a process called emulsification. Fat cells are broken down into fatty acids and glycerol, only to get built up again later, this is actually because fat cells are too fat (ba dum tss) to go through cell membranes.
White Fat – or white adipose tissue (WAT) – oh we all know what this is. We’ve all seen those 5-20lb replicas of white fat, that yellow, lumpy, oh so desirable mush. Don’t get me wrong, this fat is important, too. It cushions our bones and organs, gives up a soft exterior, but in excess it can lead to health issues. Did you know that our fat cells actually change and adapt as we gain fat? If you look at the fat cells of a lean individual vs. an obese one, you will notice that obese fat cells can carry 10x the amount of fat than a normal fat cell. An extra 30lbs may make you heavier and have a greater fat mass, but it’s not actually until individuals are obese that their fat cells actually multiply. Once we reach this status it is actually harder to get rid of fat cells, aka you may still always have 10-20 million more fat cells than a lean individual, however, they can get smaller and you will be healthier at that point. Fascinating.
White fat cells don’t just sit around like couch potatoes. They actually release hormones that can aid in keeping us healthy or making us gain weight. The key hormones in this function are leptin – a protein hormone responsible for telling you “hey stop! we’re good down here! We’ve got plenty of fat to burn and you’re full!” It’s also known as the appetite hormone – remember it’s evil nemesis ghrelin? The one your body secretes when you’re stressed? Well, imagine leptin and ghrelin up on top of a cliff like in Princess Bride, swords in hand, ghrelin advances forward “you killed my fat cells, prepare to die.” Ok – so not exactly, but if your stress levels get high enough to reach the evil perch where ghrelin hangs out, then he’s going to create an army of fat cells by stimulating your appetite.
The other protein hormone that white fat cells release is called adiponectin and it is only secreted by fat cells. This hormone helps regulate glucose levels and influences how your body reacts to insulin. It’s an extremely important hormone, the problem is that when fat cells become too big like they do in an obese body, the production of adiponectin can decrease and completely shut down in fat cells. This aids in heart disease and diabetes. Low levels of adiponectin can also lead to insulin resistance.
Brown Fat – or brown adipose tissue (BAT) – the mysterious fat many people don’t know about which acts a lot more like a muscle than a fat. This fat is essential for survival. It contains mitochondria which generate heat and explains why brown fat is found in animals in cold climates, in babies who have yet to develop white fat cells, and in individuals when they are cold. Now, I’m not here to tell you that brown fat is the miracle fat and that if you have more of it, you’ll be skinny in no time. However, brown fat has been found to absorb glucose and actually burn calories, unlike white fat. Brown fat also needs more energy to survive and will actually suck up white fat around it. Brown fat is activated when the body gets cold, it’s a survival mechanism to keep us warm. One of the most interesting discoveries that is still being heavily researched is the detection of irisin which is a muscle hormone that is released during exercise. It has been found to actually turn white fat cells into brown fat cells. Please don’t go and turn your heat off and try to shiver off all those Christmas cookies. But it is interesting to know what’s going on inside that body of yours.
There is also visceral fat and the omentum that I go into a lot more detail here.