Fasted cardio and very low-carb diets have been and continue to be touted as the best way to lose fat because of their ability to increase fat burning.
You’ve probably heard that skipping breakfast before doing cardio in the morning is more effective for weight loss than doing it at any other time of the day.
Like fasted cardio, very low-carb diets gained popularity based on the assumption that if your body doesn’t have carbs to burn for energy, it will burn fat.
It would seem logical to conclude that if your body uses fat for energy, your body will reduce fat and you will lose more weight.
But…
Fat burning is NOT the same thing as fat loss!
Fat reduction/loss and fat burning are not the same thing!
What is fat burning?
"Fat burning" refers to the body's use of fat as a fuel source.
Fat is stored in our bodies in the form of triglycerides. Triglycerides are found in the blood, in adipose tissue (fat cells), and to a lesser extent in muscle mass.
In order for fat to be used as fuel, triglycerides must be broken down into fatty acids through a process called lipolysis.
This is where the concept of fat burning comes from, which is like fat reduction. Your body takes fat from fat cells to produce energy.
However, unless you are in a calorie deficit, fat burning will not result in actual fat loss.
If you feed your body a lot of carbohydrates, it will primarily use carbohydrates as an energy source; if you feed your body a lot of fat and very few carbohydrates, it will primarily burn fat as a fuel source, this is because it is most readily available in the blood. If you consistently eat a high-fat, low-carb diet, you will have a constant supply of triglycerides in your blood and you will also have a higher rate of fat storage.
So, even though your body may be mobilising fat from adipose tissue, it is also storing fat, so your body cannot reduce the amount of fat in your body just because it has used fat cells as a source of energy. If you are not in a caloric deficit, it does not matter how much fat your body uses during activity; that fat will be replenished throughout the day.
