Have you ever been in an elevator with someone who is overweight? You may have heard that person breathing. Fairly loudly. Not all do, but it is often true. I say this with no disrespect to the overweight; more just to illustrate my point. Why are they breathing this loudly? A similar outcome can occur when you run, walk briskly or exercise. What is the underlying physiology happening in your body than is making you breathe deeply or pant?
Your body needs oxygen to function. In an amazing process oxygen, twenty-one percent in volume terms enters your body along with nitrogen. Transfer of oxygen takes place to your body from your lungs through the lining of your cells. The oxygen then bonds with your haemoglobin and is transferred to the rest of your body. Here is where it gets fascinating. If you are overweight, you are carrying more cells, especially fat cells, in your body. The extra cells in someone who is overweight require additional oxygen as each cell is constantly undergoing metabolism. The lungs, therefore, need to take in extra air to compensate for the need for oxygen. It is this that is making the person pant even without exercise. Often, this sounds like deep breathing though, in truth, it is not. It is simply your body trying to maintain the balance of essential gases in your body.
Similarly, when you exercise, the rate of depletion of oxygen is faster than the rate of intake. Your body goes into oxygen deficit causing you to breathe deeper to take in more oxygen. This, an outcome of exercise is beneficial as over time it causes your lungs to expand to expand to cater to the need for additional air. The outcome is a healthier lung and heart. If at all you are panting, surely you want it to be due to exercise not weight?