Key question: Does exercising before (versus after) breakfast often benefits for my health?
As we have mentioned in a few posts, exercise is recommended to help people manage their body weight and to reduce the risk of type 2 diabetes and cardiovascular disease. However, some people feel they don’t have the time to exercise frequently, so as health scientists we are interested in whether we can increase the benefits of exercise that is performed (i.e. get a bigger bang for your buck!!) This was the basis of my PhD.
The main study of my PhD looked at the health responses to six weeks of exercise training, which was fully supervised cycling for 50 minutes, three times a week (which aligns to current exercise guidelines). The exercise was moderate intensity cycling, so these results are relevant to moderate-intensity physical activity, such as walking, running or cycling and not necessarily high-intensity exercise or weight lifting.
In one group, overweight or obese men exercised before breakfast (in the fasted state) and these men showed an improved blood insulin response after the training. So at the end of the training, they had to produce less insulin to control their blood sugar, which is a good thing for diseases such as type 2 diabetes, as we know from Article #7. However, the men who performed the same exercise after eating breakfast did not show an improved blood insulin response. We gave the men the same breakfast and they performed the same amount of exercise. So by only changing the timing of their meals there was a difference in their health responses to this exercise training (pretty interesting, right?)
We also measured some adaptations in the exercised muscle and we found that proteins that are involved in adaptations (a protein called AMPK) and sugar transport in muscle (the protein known as GLUT4 that we learnt about in Article #7) also increased with exercise before versus after breakfast. This suggests that there are additional health benefits of doing some exercise in the fasted state and supports a study that was conducted in healthy men.
Whilst more research is needed in this area, we currently think that these increased health benefits of doing exercise before breakfast could be linked to increased fat burning.
What about body weight?
In terms of other health benefits such as increases in fitness or changes in body-mass and -composition there were no clear differences between the men exercising before versus after breakfast. For changes in body weight, this is probably because there were no differences between the two groups for changes in their overall energy intake or energy expenditure. For more information about energy balance click here. Some of my other research showed that if you skip breakfast completely and do exercise you might be able to maintain a more negative energy balance in the short-term (you don’t compensate for skipping breakfast by eating more later in the day or being less active). This could be beneficial for long-term changes in body weight, although more research is needed to confirm that.
Do these results apply to everyone?
We still need to conduct a study with women, however we think that the increased health benefits of exercising before breakfast are linked to greater fat burning and men and women both burn more fat with fasted (versus fed) exercise. Therefore it is very likely that we would see the same response in women. Interestingly a recent study looked at exercise before breakfast in men who already had type 2 diabetes and found results that differed to mine. This may be because those researchers didn’t measure blood insulin levels (they looked at average blood sugar levels over a longer period) or it could be because they studied a different population to my research.
Take home message: Exercising before breakfast can offer some increased health benefits in overweight or obese and healthy people, including improving the insulin response to blood sugar and for adaptations in the muscle. However, for weight loss, if you only change the timing of your breakfast, you may not see greater losses in body mass. To stay up to date and receive an email when a new article goes live... click here!!