When you take steps to change your physique, especially when that change results in body fat loss, people tend to notice it. Beyond congratulating them on the change, have you ever wondered where the body fat has gone?
The surprising answer (for those outside the healthcare industry) is that we breathe it in. This is why increasing your heart rate, thereby increasing your respiratory rate, is so effective in burning body fat, especially visceral and subcutaneous fat. These types of fats are stored energy – energy that you have ingested but not used.
The easiest way to understand the concept is calorie intake, calories expended. Calories in refer to the number of calories – a measure of energy – that you get from the food you eat, while calories out are the number of calories you burn. If your calorie intake is more than your total daily energy needs, your body will store the excess energy as body fat for use when it needs it.
We tend to think of the macronutrients in our diet – fat, protein, and carbohydrate – as fuel for our bodies, and that’s true, but that’s an oversimplification. No matter what we eat, our food is just unrefined fuel. Think of it like crude oil. If you put crude oil in your car’s gas tank, you won’t get far. Fortunately for us, our digestive system is not like a car’s gas tank. It’s more like an oil refinery, which takes the unrefined energy we’ve eaten, breaks it down, cleans it, and sends it into our cells for use.
Our cells use a special type of fuel called adenosine triphosphate, or ATP. ATP is to our cells what gasoline is to a car engine. It is our refined fuel. The combustion of gasoline, ignited by the spark plug after compression by the piston, generates the energy necessary for the power of the engine. In our bodies, however, energy is released when chemical processes cause ATP to lose its third phosphate, turning ATP into adenosine diphosphate, or ADP. ADP can be “recharged” with a third phosphate to become ATP again.
Our bodies use a process called cellular respiration to produce ATP from the glucose in our food or stored energy stores and the oxygen we breathe. This process also produces carbon dioxide and water. Our body uses water until it is lost as urine or sweat. The carbon dioxide is transferred to our blood, which brings more oxygen to our cells, and our blood then brings the carbon dioxide to our lungs to be exhaled.
This whole process is the reason why aerobic exercise is so effective in helping us burn body fat. When we move our muscles, they need more ATP. Our heart and respiratory rates increase to provide the ingredients needed to combine with glucose from our diet or our body’s stored energy stores to create ATP and remove the resulting carbon dioxide.
This cycle is also the reason why it is possible to lose body fat through a change in dietary lifestyle. Right now, your body is burning calories because you are alive. Your cells are consuming energy, but not as fast as they would be if you were in the middle of the exercise. But if exercise isn’t for you, you can still lose body fat by creating a calorie deficit. You do this by eating fewer calories than your body needs, and this is best accomplished with foods that are nutrient dense and less calorie dense. A deficit of 500 calories per day will usually result in the loss of one pound of body fat per week.
It is important to make sure that you are not starving yourself, as your body will create and hold energy if it thinks it is starving. This is why nutrient rich foods are essential for dietary weight loss. And the same goes for a conversation with your doctor.
Ultimately, food is fuel. You will use or store its energy. When the energy is used up, a good part of it will be exhaled. The human body is a truly remarkable machine.