Is it better to eat before or after exercise?

Dr Joan Ransley

We all know exercise is good for us. It strengthens weak muscles and improves cardiovascular and respiratory health. If we are fit, we can do more physical and mental work and are less likely to get ill.

Fitting exercise around meals, working, and looking after a family is challenging. So, it is important to know how to maximise the benefits we get from the exercise, whether it’s jogging, swimming, or lifting at the gym. 

One question that is commonly asked is - is it better to exercise before or after a meal? 

The short answer is that both exercising before and after a meal can be good for health. Here’s why. 

Exercise and its influence on blood glucose levels

There is evidence that the timing of exercise has a big effect on blood glucose levels. 

Glucose circulating in the blood comes from the food we eat. It is either used by muscles for exercise or stored away for later use. Studies have shown that glucose uptake in the muscles can be 50 times faster when we're exercising compared to when we're sedentary. This is a big effect and can improve blood glucose control. So, for this reason, doing some exercise after eating is a good thing. It can help reduce the risk of developing type two diabetes. A common, serious disease. 

So, when is the perfect time to eat to reduce blood glucose peaks?

Blood sugar peaks at about 30 to 60 minutes after a meal. Exercising between 30 to 45 minutes after a meal, can efficiently blunt blood glucose surges.

Does exercising before eating have any benefits?

Yes, it has two main ones. It increases the amount of fat the body burns, and it can improve insulin sensitivity. 

Burning fat while exercising

Studies have shown that people who exercised before eating breakfast burned about double the amount of fat than people who exercised after breakfast. This can be good for cardiovascular health.

Does this mean burning fat will help me to lose weight faster?

It is a common misconception that burning fat through exercise will lead to weight loss. There isn't a lot of good evidence to show that exercise, either before or after you eat, is a reliable way to lose weight. But exercise can certainly help to stop you gaining more weight.

Exercise and insulin sensitivity

Exercising before eating breakfast has been shown to increase insulin sensitivity.

Insulin is a hormone that is released from an organ known as the pancreas. Its main action is to transport blood glucose into muscle cells. People have very different sensitivities to insulin. If you are not very sensitive to insulin, (this includes many people who are overweight or obese) you'll need to produce more insulin to move glucose from the blood into their muscle cells. Someone who has low sensitivity to insulin is at risk of developing type two diabetes. 

Scientists think there may be a link between this increased insulin sensitivity, increased fat burning post exercise and better health outcomes.

So, what's the verdict? Should you exercise on an empty stomach or have breakfast first?

There are some benefits to exercising both before and after you've eaten. It can be difficult to undertake vigorous exercise just after eating but taking gentle to moderate exercise up to an hour after eating can have an immediate beneficial effect on lowering blood sugar peaks. 

For longer term improvements in health from exercise training, it can be useful to do at least some exercise before you have breakfast because it improves the insulin response and increases fat burning.

Is there enough energy in the body a typical exercise session?

Yes. If we're eating a normal diet, we've got enough energy to fuel a typical exercise session of up to an hour or even an hour and a half. Most people will have enough fuel in their body from the food eaten the day before.