Stored Fat Is A Accomplishment Of Evolution And Your Body Will Fight To Keep It

In spite of the bad press, stored fat is actually a really wonderful thing. Without the capacity to store energy in the form of fat, we would have been unlikely to survive through millions of years of evolution and we would certainly appear most varied to the route we look today. We needed the capacity to store energy to survive periods of famine, and fat is a very sensible route to do this.

Even a relatively lean 75 kg human typically has over 100,000 kcal stored in the form of fat. If we had to store this energy in other forms for example as glycogen, the storage form of carbohydrate our weight would increase by 40 -6 0kg( because glycogen is less energy dense and also stored in combination with water ). Imagine dragging around two packed suitcases while hunting or gathering and youll get the idea of why it has been so useful to package stored energy in the form of fat.

So, while fat is often demonised, it has also been our friend through millions of years of evolution. It builds sense for our bodies to store energy in this way and to develop systems to cling on to it simply in case there is a famine around the corner.

But, our relationship with fat has changed. While some fat is essential and healthy, amassing too much body fat has a detrimental impact on our health by increasing the risk of chronic illness. So, storing too much energy in the form of fat is clearly not a good thing. Sadly, most people are now storing too much energy as fat and many people in the developed and developing world are now considered overweight or obese.

Difficult to let go

Excess stored fat is a particularly difficult problem to solve in part because we have evolved such sophisticated process to protect fat stores once we have them.

One of the best-characterised physiological systems involves leptin, a protein secreted by our fat stores( adipose tissue) that tells the brain that there is plenty of energy available stored in the form of fat. When discovered, there was a great deal of excitement about whether leptin could be administered as a therapy for obesity perhaps in an injection that would trick the body into thinking that there were large amounts of fat available so that we do not eat as much. Sadly, these potential therapies were not effective and we now understand why.

As we store more and more fat the leptin level in our blood will increase in proportion to the increase in stored fat. Our brains get used to this higher level of leptin, so administering more leptin over and above this higher level of leptin does not seem to help. Instead, it is when leptin levels fall that leptin becomes a very important signal. When we try to lose weight, there is a disproportionately large autumn in circulating leptin in spite of merely modest fat loss.

A fall in leptin is an attempt to defend fat stores with leptin functioning as the signal to the brain in a negative feedback loop that maintains the stability of fat mass. A fall in leptin is associated with increased sensations of hunger and an increase in reward-related behaviours. Reduced leptin is also a trigger for depressive symptoms in animals. So, when we try to lose weight, our fat tissue sends signals to the brain to try to defy any further loss of fat; we feel hungry, we seek rewards, and we might feel a little down or depressed.

^{Not guaranteed to work if your hormones have anything to do with it. Weight loss by Shutterstock}

What can we do about this? Well, a recent study indicated that fat tissue may have some other properties that we might be able to manipulate to assist. Some specialised types of fat cells( adipocytes) have the ability to burn energy to help keep us warm( a process called thermogenesis ). The writers showed that this type of thermogenesis is normally turned off by a specific protein called sLR1 1. This builds sense because for millions of years we have been striving to store fat and merely use it when there is a very good reason.

Interestingly, in this study, mouse created without sLR1 1 did not gain weight when overfed since they are burned more of the energy that was consumed. The writers also showed in a small number of patients undergoing bariatric surgery that the fall in sLR1 1 was related to the decrease in fat mass. Based on these observations, they suggested that sLR1 1 stops energy from being wasted via thermogenesis in fat tissue. By inference, if it is possible to turn this off in humen then we might be able to get the body to use( trash) energy rather than clinging on to it.

Before we get too carried away, a caveat here is that this type of thermogenesis is mostly confined to certain types of fat cells( brown adipocytes or brown fat) and these cells are more rare and probably less important in humen than in rodents. We can also achieve thermogenesis through other means such as burning energy through motion. We know that increasing thermogenesis through motion leads to a fall in leptin and that this probably explains why training exercises program causes people to eat more and not lose as much weight as they should. Whether burning energy through increased adipose thermogenesis will have the same effects in humen still also needs to be established.

So, for now, it is important to remember that when “youre feeling” yourself gaining a few pounds, your body will see this as a success and it will oppose hard to keep any extra weight.

Stored Fat Is A Accomplishment Of Evolution And Your Body Will Fight To Keep It

Stored Fat Is A Accomplishment Of Evolution And Your Body Will Fight To Keep It

Stored Fat Is A Accomplishment Of Evolution And Your Body Will Fight To Keep It

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