ROB EDINBURGH, THE CONVERSATION4 NOV 2019
Our latest research has found that you might be able to get away with doing less exercise if other commitments, such as family and work, always seem to get in the way.
To explain how this works, it helps to know a bit about insulin. Insulin is a hormone that helps control blood sugar levels. One of the main effects of insulin after a meal is to allow sugar in the blood to be transported into muscle, where it can then be stored or used as a fuel for energy.
When people don't exercise enough and become overweight or obese, their bodies have to produce more insulin for the hormone to have this important effect. In other words, they become less sensitive to insulin. This is one of the reasons why being overweight increases the risk of getting type 2 diabetes and cardiovascular disease.
One of the main health benefits of exercise is that it improves our response to insulin and we can better control our blood sugar levels – even if we don't see this change happening. It is now becoming clear that when we eat in relation to exercise could be important for this insulin response.
Our study looked at the responses to six weeks of exercise, which was supervised cycling for 50 minutes, three times a week. In one group, overweight or obese men exercised before breakfast (fasted state) and showed an improved insulin response after the training. That is, they had to produce less insulin to control their blood sugar levels.
This suggests that they had a lower risk of diseases such as type 2 diabetes after the training. But the men who performed the same exercise after eating breakfast did not show an improved blood insulin response.
The men who exercised before breakfast also burned about double the amount of fat during exercise than the group who exercised after breakfast. Current evidence suggests that this increased fat burning during exercise may explain why that group showed improved health benefits.