Exercise, inflammation, and fat – the good, the bad and the ugly

Systemic inflammation is a condition in which the body’s immune system is hyper activated. Inflammation is a normal reaction which occurs after the body has experienced some sort of trauma, for example a papercut. When you’ve cut your finger, local inflammation occurs, the finger will turn red, warm, swollen and it will be a bit sore. This reaction is caused by a local increase in pro-inflammatory immune molecules (immune molecules are called cytokines). Inflammation is therefore a necessary evil to fight off a potential infection from pathogens. However, sometimes there is an increase in these pro-inflammatory cytokines in the entire body. This hyper activated state is called systemic inflammation. People who suffer from this chronically are at risk for a number of diseases, such as, type 2 diabetes, cardiovascular disease, depression and dementia.

We know that one important cause of this chronic systemic inflammation is fat. Fat has two forms, subcutaneous and visceral, depending on where it is stored. Subcutaneous fat is stored below the skin and visceral fat is found around the organs and in between the muscles. It is in our visceral fat that impacts developing the above-mentioned diseases. This might seem a bit weird, fat is fat, right? Well, not when you go digging down into the immune cells. The visceral fat of obese patients has more macrophages, T cells and inflammatory molecules. In essence, the visceral fat of these people is pro-inflammatory. The only exact way to determine someone’s proportion of visceral fat is doing a full body scan. This is obviously a very expensive technique. An easier way to determine if someone is in the at-risk group is to measure the waist circumference. The National Health Service in the UK uses a cut-off of 94cm (37 inches) for men and 80cm (31.5 inches) for women. So everyone who has a waist circumference above this cut-off is considered at risk for those diseases. Bad news for the Irish, given the predictions for 2025.

A great way to reduce this inflammatory response is through exercise. Firstly, exercise is good for reduction of the overall fat mass, including the visceral fat tissue. Reducing this will also reduce the amount of pro-inflammatory cells that are being harboured within. Secondly, exercise without weight loss is still beneficial through the reduction of pro-inflammatory cytokines and the increase of anti-inflammatory cytokines. During exercise, the body first produces a pro-inflammatory cytokine called interleukin (IL)-6. IL-6 can be produced in several circumstances, when it’s produced in combination with another cytokine called TNF-α, it becomes a major player in the development of type 2 diabetes. However, IL-6 without the presence of TNF-α, as seen during exercise, has beneficial effects. IL-6 will first rise fast during exercise and drop back to normal levels an hour after. It is this rise, and subsequent fall, of IL-6 blood levels that the body starts producing anti-inflammatory cytokines (IL-10 and IL-1Ra). This interplay gives positive effect.

A side effect of this can be found in elite athletes. Some athletes suffer from repeated upper respiratory tract infections, probably due to the fact that they have so much anti-inflammatory cytokines that their immune system is slightly impaired.

So although not everyone might experience exercise induced weight loss, exercise is still a critical part of the immune system in controlling a wide range of chronic diseases.

Gwendoline Deslyper