- The 'personal fat threshold' hypothesis
- The body's key energy systems regulating both fat and carbohydrate that will influence our personal fat threshold
The key message so far has been that the body's ability to store fat in the form of subcutaneous fat in the adipose tissue (i.e. the fat stored underneath the skin) protects the body from harm. As a reminder, this process makes sure that:
- Excess energy doesn't build up in the cells
- Excess energy doesn't build up in the bloodstream
- Fat isn't stored within the internal organs
The main focus of these articles has been point number 3, as this appears to be the 'tipping point'. When fat storage begins to increase in the internal organs, chronic diseases such as type-2 diabetes start to develop or accelerate.
This article will explore how the adipose tissue holds the key to identifying where your 'tipping point' (aka your personal fat threshold) will be, and how insulin, and specifically insulin resistance, influences this process.
- The storage of fat in the adipose tissue is a protective mechanism against excess fat being stored within the internal organs
- You could describe the point when more fat starts to be stored within the internal organs as the 'tipping point' in your personal fat threshold
- Going beyond this tipping point is when type-2 diabetes and other chronic disease are more likely to develop or accelerate
Adipose tissue: increase in size vs number
In part 2, we discussed how your adipose tissue can store excess fat through either increasing the size of existing fat cells (hypertrophy), or increasing the number of new cells (hyperplasia). As a reminder, this is displayed in the image below.
Research has shown that people who gain weight by increasing their fat cell number (hyperplasia) compared to increasing their cell size (hypertrophy), are less likely to develop insulin resistance and chronic diseases such as type-2 diabetes. It appears that storing excess fat by increasing the number of fat cells causes less harm to the body than increasing the size of existing ones.
The volume of fat cells that your body can produce appears to reach its peak in your late teens and is influenced by your genetics. However, research has shown that this can also be influenced by lifestyle factors such as diet and exercise (i.e. by leading a healthy lifestyle you may improve your body's ability to grow new fat cells, and therefore, reduce your insulin resistance).
Why is hypertrophy of fat cells more detrimental to health?
Firstly, there's only so much fat that an individual cell can store. If your body is unable to produce new adipose tissue cells to store fat in times of excess energy intake, then your capacity will be limited to the current number of fat cells you have in your body.
Secondly, research has shown that as fat cells increase in size, they become more dysfunctional and start releasing pro-inflammatory products into the bloodstream which can increase inflammation (damage to cells) and cause insulin resistance in the muscles and the adipose tissue.
We briefly discussed insulin in part 1 and part 2 of this series. Insulin resistance is where your body's cells no longer respond to insulin, leaving the insulin unable to instruct cells to take in energy from food (i.e. glucose into the muscles cells or fat into the adipose tissue).
So far, our focus has been on where the body is able to store fat (i.e. subcutaneous under the skin or in the internal organs), and how this can predict your risk of developing type-2 diabetes. It's also evident that how your body stores fat will have a big impact on your personal fat threshold.
As we mentioned above, there will be many factors influencing how your body stores fat (i.e. whether it increases existing cell size or increases cell number), including genetics, your diet, and your levels of exercise.
- Adipose tissue has two ways it can store excess fat: hypertrophy (increase in cell size) and hyperplasia (increase in cell number)
- Storing excess fat through an increase in cell number (hyperplasia) has been shown to be protective against developing insulin resistance and type-2 diabetes. Although this is largely influenced by your genetics, diet and exercise also regulate this process.
- Storing excess fat through an increase in cell size (hypertrophy) increases insulin resistance in the body and your risk of developing type-2 diabetes
- Insulin resistance occurs when your body's cells no longer respond to insulin and are unable to take in energy to store or burn
As we've discussed in part 1 and part 2, insulin plays a key role in the regulation of both fat and carbohydrate. When your body's insulin levels are high, your rate of fat storage will increase and your body's cells (i.e. in the muscles or the heart) will use more glucose for energy. When insulin levels are low, your body will store less fat, and use more fat for energy.
This cycle is important for our health. Our body prefers to be in a constant cycle of efficient fuel storage and usage. Consider this 'energy flux', which refers to how quickly your body can move energy from the bloodstream into the cells for storage or to be burnt for energy.
If your body becomes insulin resistant, and fat or carbohydrate can no longer enter the muscles or the adipose tissue to be stored or burnt, it's more likely to build up in the bloodstream, and your body will be forced to try and store it in your internal organs.
If we think back to part 1 and how carbohydrates are regulated, insulin's role is to move glucose out of the bloodstream and into the cells to either be stored as glycogen or burnt for energy. If you're insulin resistant, the cells can do neither, and the excess glucose must be transported to other areas of the body to be stored as fat.
As mentioned above, your adipose tissue can also develop insulin resistance and it becomes difficult for fat or carbohydrate to enter the adipose tissue for storage. If this occurs, alongside your muscle cells being insulin resistant, then your body has no choice but to transport the excess energy to your internal organs.
Your organs will also have a limit to how much energy they can store and will also develop insulin resistance over time. It's at this point that excess energy (i.e. glucose) will build up in the bloodstream. This appears to the basis of many chronic diseases such as type-2 diabetes.
The main way we measure type 2 diabetes is HbA1c. This measures the volume of glucose that is bound to your red blood cells, and therefore gives an indication to the total volume of glucose in your bloodstream.
It's a sign that your body's last lines of defence against 'energy toxicity' have failed. Where your body, due to a variety of reasons, is no longer able to store and burn energy properly. Therefore, this energy finally builds up in the bloodstream.
Type-2 diabetes is a condition that is categorised by insulin resistance. It's likely that your level of insulin resistance in your muscles, adipose tissue, and organs is the defining characteristic of your personal fat threshold.
- Insulin plays a key role in the regulation of fat and carbohydrate
- Your body wants to be in a constant cycle of storing and burning energy (i.e. it requires periods of lower insulin)
- When your body is insulin resistant, your cells no longer respond to insulin, and they're unable to take in energy to store or burn for energy
- Insulin resistance appears to be the underlying issue influencing the personal fat threshold
Can you improve your personal fat threshold?
While many elements of our personal fat threshold will be influenced by our genetics, it's clear that insulin resistance is the underlying condition that will determine when you reach this point.
And while we may not have the research to support strategies to improve (or increase) your personal fat threshold, we have plenty of research that has shown us how to reduce insulin resistance and improve the function of your body's energy systems, which we'll be discussing in part 4.
Take home message
It appears that underlying every individual's personal fat threshold is their level of insulin resistance. Although it may be difficult to 'diagnose' or identify an individuals personal fat threshold, we're able to identify their level of insulin resistance (through several diagnostic tests such as HbA1c).
Lifestyle changes such as diet, exercise, stress management, and sleep are all proven strategies that reduce insulin resistance and can improve the function of the body's energy systems. This is why we have a holistic approach to health on Second Nature, it all plays a part!
In part 4, the final article in this series, we'll discuss the key lifestyle factors that influence your insulin resistance and how can improve them, and therefore, your personal fat threshold.
Article written by Robbie Puddick, Registered Nutritionist and Second Nature Health Coach