Burning Body Fat 101
Understanding how fat is used as a fuel (ie. burnt) is essential to building a personalised strategy to improve body composition. Once understood, it becomes easier to see how exercise and nutrition selections impact fat usage and subsequently lead to body composition changes.
There are three steps that fat must go through to be burnt: mobilisation, transportation and oxidisation. Here is a brief description of each step.
Stage One: Mobilisation
The first and most important step in the process is the mobilisation of fat. The fatty acids are released from the fat cell and then deposited in the bloodstream for transportation. This occurs when cells (such as muscle or heart cells) require fuel for energy and the body signals for the release of stored energy from fat tissue.
Fatty acid mobilisation can be enhanced by the release of two catecholamines - adrenaline and noradrenaline - which occurs during exercise. As exercise intensity increases, so do the catecholamine response. High-intensity training (resistance training, interval training, basically anything that gets the heart rate up!) provides the greatest catecholamine response, and consequently mobilises a lot of fatty acids!
Stage Two: Transportation
The fatty acids must then taking to the cell that needs them for energy production (let’s say the biceps #armday). The transportation of fatty acids relies on blood flow to get from the fat cell to the target cell. Exercise enhances blood flow and ensures blood is directed to the working muscles.
Fatty acids don't mix well with blood (water-based) in a manner similar to olive oil and water mixing together. As a result, fatty acids bind to albumin - a serum protein - for transportation in the blood.
Exercise selection is an important consideration for blood flow. Seated activity such as bikes can partially compromise blood flow between the upper and lower body, because of the positioning, pressure on blood vessels and lack of upper body contribution. As a result, the elliptical is actually a great cardio machine for maximising blood flow.
Stage Three: Oxidation
If you are looking to lose fat, well this is where the magic (or science, if you prefer that) happens!
Once the fatty acids reach the cell that requires energy, they are oxidised and converted to usable cellular energy adenosine triphosphate (ATP) along with the byproducts such as carbon dioxide (which you then breathe out). This process is extremely efficient and provides a high yield of energy for the cell.
Yay! The fatty acids are burnt and we can all live happily ever after. Well not quite...
The Contradiction
Fat is predominately used as a fuel at low intensities, where the body can utilise sufficient oxygen to oxidise the fatty acids. This tends to be up to 60% maximal intensity, so think walking and jogging. When the intensity increases, the cells turn to carbohydrate fuel sources that can be used without oxygen (ie. NOT oxidised) which provide more rapid energy in a less efficient manner.
Now, why is this an important piece of information?
Fat is used as a fuel at lower intensities but fat mobilisation is optimal at higher intensities, due to the catecholamine response. So even though fat is getting mobilised during high-intensity training, it isn’t necessarily getting oxidised straight away. However, when you stop training and return to rest, your body can now oxidise these mobilised fats at a lower intensity.
If only there was a way to get the best of both worlds...
A Smarter Approach
We can take advantage of this process by prioritising high-intensity exercise early in a workout and then transitioning to lower intensity exercise towards the end of a session. This allows the client to mobilise fat early on, and then maximise the amount that can be oxidised through lower intensity exercise.
This training method also allows the programming of both strength and fat loss training within the same session. There's no need to train twice per day when you can combine the two for maximal fat burning results!
We can also play around with nutritional timing, some supplementation and other training methods. There is no need to over-train or under-eat to burn fat and lose weight. Just focus on the basics and then incorporate some more advanced methods once the foundation has been put in place.
A good nutrition plan and consistent exercise are all that you need to get started. However, if you want to get a little more out of your training and nutrition for fat loss, incorporate these little tips to ramp it up!
