The Science of Fat Loss Part 2: Break Fat Free from the Cell
In order for you to lose body fat, three main things need to happen, each with their own specific steps that can inhibit or increase the odds of body fat being lost. During this post, I will talk about the first and possibly the most important step in fat loss.
The most important step for fat loss = Fat must be released from the fat cell.
This means fatty acids are released from the fat cell and into the blood stream. For this to occur, two main things need to occur:
A – Insulin and overall glycogen levels have to be low.
B – Hormone Sensitive Lipase (HSL) has to be activated, primarily through cyclical adenosine monophosphate (cAMP). Adrenaline and nor-adrenaline, also known as catecholamines, help to activate HSL and therefore increase the rate of which fat is released from the fat cell.
When fat is released or broken away from the cell (after HSL is activated), the fat cell is broken into its two component parts, glycerol and triglycerides. Glycerol, as you can see from the picture above is the component that holds the three fatty acids (hence the term “tri” in triglycerides) together. The triglycerides are like amino acids to protein or glucose for carbs. In other words, this is the smallest part of the molecule of fat your body can actually use for energy.
Once your fat cell releases triglycerides into the blood stream, your body can then transport those fatty acids (step 2) to be used for energy (step 3). Both of these mechanisms will be discussed in part 3.
In order for those last two steps to happen though, this first step of the triglycerides being released from the fat cell needs to occur. For this to happen, your body has to have a reason to release that fat.
So what are some reasons that your body will have to release that fat?
Mainly if insulin levels are low (this is why uncontrolled high blood sugar and type 2 diabetes is so bad for your health) and if there is not a large amount of fat circulating in your blood (high triglycerides, either from consumed fat or carbs converted into triglycerides in the liver). Therefore, if you go about eating every 2-4 hours, your body will release insulin every 2-4 hours in response to your food intake. If there’s high circulating fat, then your body will also send signals telling you that you have no reason to release fat, because you already have fat in your blood stream that can be used for energy.
Insulin though is generally the hormone most responsible for inhibiting HSL. If you inhibit HSL, fat mobilization (or fat breakdown from the cell) will be low. If HSL is high, then you increase fat breakdown.
Therefore, for you to even breakdown fat, insulin levels have to be low. If on the other hand, insulin levels stay high, no fat breakdown will occur. Insulin signals to your body that you don’t need to use fat for energy because there’s glucose in the blood. Glucose in the blood is toxic and insulin helps the body utilize that glucose. Glucose ends up in one of four fates:
1 – Into cells (either fat or muscle cells)
2 – Stored as Muscle Glycogen
3 – Stays in the blood and causes high blood sugar (a bad thing)
4 – Gets converted in the liver into a Triglyceride (gets converted into fat)
Therefore, for you to breakdown fat, you either have to not be eating often and be in a caloric deficit. The reason for this is because of the second step for fat breakdown to occur, HSL has to be activated.
You see, if you’re in a calorie deficit, you will start to increase your catecholamine levels (adrenaline and nor-adrenaline levels). By doing so, you activate HSL, which tells your body to breakdown more fat for energy. This occurs with high intensity exercise and pretty much anything that increases adrenaline and/or nor-adrenaline.
If that was all there was to the fat loss equation, fat loss would be pretty simple. As we’ll see, there are a number of other factors that make the equation much more complicated.
Fat Mobilization (Fat Breakdown from the cell and into the bloodstream) = Low HSL (Low circulating Insulin/Triglyceride levels) + High HSL (Adrenaline and Nor-Adrenaline)
cAMP activates HSL which tells the body to breakdown fat into Triglycerides and Glycerol. Triglycerides are the part of fat that your body can use for energy.
Adrenaline and nor-adrenaline tell HSL to become activated and therefore tell your body to increase the mobilization of fat from the cell.
Adrenaline and nor-adrenaline are very similar in structure, except one is a hormone that travels through your body in the blood (adrenaline) and one only acts in the area between two cells (nor-adrenaline).
This is where we’re at so far.
Different Receptors have Different Reactions
Almost all cells have receptors for catecholamines, but there are different types of receptors. In this discussion, we’ll focus only on Alpha and Beta adrenalin receptors. Those different receptors, along with different ratios of those receptors, cause different reactions.
For example, some receptors (Beta) increase the rate at which fat mobilization occurs. Other receptors (Alpha) actually blunt or inhibit the mobilization of fat. This is despite the fact that adrenaline and nor-adrenaline is the key activating them both. In other words, the same hormone/neurotransmitter is being released, which causes completely opposite reactions depending on the receptor (and ratio of receptors) present on the fat cell.
The amount and ratios of these receptors in various body parts influence how “stubborn” body fat is.
Beta receptors tell your body to burn fat. Therefore, Beta receptors are good for fat loss, whereas Alpha receptors are bad for fat loss.
Lyle McDonald in his book Stubborn Fat Solution explains why it’s hard for so many women to lose fat around the thighs, when he say that thigh fat has 9 times as many Alpha receptors than Beta receptors. In other words, even if all the conditions are right (low insulin, high catecholamines), fat may still not be released from the cell, therefore making that last amount of fat still hard to come off.
On the other hand, if you remember from part 1, visceral fat has a lot of Beta receptors which helps to make visceral fat one of the first places that fat comes off. Abdominal fat has about an even number of Alpha and Beta receptors, which makes it difficult, but not impossible for the fat to come off of.
So a quick recap of this last part:
Alpha receptors are bad for fat loss, as they slow heart rate, decrease blood pressure and generally lead to fat storage. Beta receptors are good for fat loss as they speed up heart rate, increase blood pressure and lead to fat mobilization.
As a quick aside, if you’ve ever known anyone on Beta-Blockers, what they are essentially doing are blocking these beta receptors so even when adrenalin is released, the person on beta blockers won’t have huge spikes in heart rate and blood pressure.
In part three, we’ll review the other two parts of short-term fat burning and in part 4 we’ll get into some of the hormones that influence long-term fat stores, such as Leptin, Thyroid, etc.
If you have any questions, feel free to leave a comment below.