How does eating before a workout affect the body?

Do you prefer to eat breakfast first then do your morning fitness routine, or do you skip breakfast altogether? Researchers from the United Kingdom look at how eating versus fasting before exercise can affect a person's metabolism and workout.

The scientists, who hail from several prestigious academic institutions in the United Kingdom — the Universities of Bath, Birmingham, Newcastle, and Stirling — looked into how eating a morning meal before cycling for an hour would affect the body versus the effects of fasting before cycling.

The findings — reported in the American Journal of Physiology: Endocrinology and Metabolism — indicate that eating first actually helps the body burn more carbohydrates during exercise.

Not just that, but having breakfast before a morning cycle can actually also help digestion after a workout, the study suggests.

"This is the first study to examine the ways in which breakfast before exercise influences our responses to meals after exercise," says co-lead researcher Dr. Javier Gonzalez.

"We found that, compared to skipping breakfast, eating breakfast before exercise increases the speed at which we digest, absorb, and metabolize carbohydrate that we may eat after exercise."

Dr. Javier Gonzalez

What happens if you eat before exercising?

For this study, Dr. Gonzalez and colleagues recruited 12 healthy male participants. To obtain control measurements, the researchers asked the study participants to have breakfast and then rest for 3 hours.

For the experiment itself, participants had a breakfast of porridge with milk, and 2 hours after this, they joined a workout that consisted of cycling for an hour.

After both the resting and exercising period, the scientists assessed the participants' blood glucose (blood sugar levels) and levels of muscle glycogen, a type of carbohydrate.

The researchers revealed that by having breakfast before their workout, the participants' bodies burned carbs at a faster rate during exercise. In addition to this, eating prior to exercise seemed to also stimulate digestion post-exercise and boost food metabolism.

"We [...] found that breakfast before exercise increases carbohydrate burning during exercise, and that this carbohydrate wasn't just coming from the breakfast that was just eaten," notes study co-author Rob Edinburgh, "but also from carbohydrate stored in our muscles as glycogen."

"This increase in the use of muscle glycogen may explain why there was more rapid clearance of blood sugar after 'lunch' when breakfast had been consumed before exercise," Edinburgh adds.

Previous studies may not be 'representative'

The researchers also note that their recent findings underline an important aspect when it comes to drawing conclusions about health outcomes based on studies about the effects of exercise.

Many studies, they say, look at the effect of exercise on people who fasted before the workout and draw their conclusions based on that. However, they explain, the results may differ if the participants are allowed to eat prior to working out.

Dr. Gonzalez goes on to point out, "Whilst fasting prior to laboratory trials is common in order to control for baseline metabolic status, these conditions may preclude the application of findings to situations most representative of daily living, because most people are not fasted during the day."

As for this study, the research team notes that while its findings are compelling, further research that will assess the long-term effects of exercising after a meal needs to be conducted.

"As this study only assessed the short-term responses to breakfast and exercise, the longer-term implications of this work are unclear, and we have ongoing studies looking at whether eating breakfast before or after exercise on a regular basis influences health," says Edinburgh.

At present, the researchers want to look at how different types of food may affect the impact of exercise, especially on individuals with various metabolic conditions such as diabetes.

"In particular," continues Edinburgh, "there is a clear need for more research looking at the effect of what we eat before exercise on health outcomes, but with overweight participants who might be at an increased risk of type 2 diabetes and cardiovascular disease. These are some of the questions we will now try to answer."