Eating breakfast before the gym or your morning run not only increases the amount of carbohydrates burned while exercising but it can also speed up digestion after working out, researchers have said.
The findings come after academics studied the effects of eating breakfast versus not eating breakfast before an hour's cycling.
The scientists also did a controlled experiment where breakfast was followed by three hours' rest and volunteers ate porridge two hours before working out.
Twelve healthy male volunteers took part with the experts testing their blood glucose levels and muscle glycogen levels after exercise or rest.
The scientists from the University of Bath – who worked with researchers from the universities of Stirling, Newcastle and Birmingham – found eating breakfast sped up how fast the body burned carbohydrates during exercise.
They also found the rate at which the body digested and metabolised food eaten post-workout also increased.
PhD student Rob Edinburgh said the carbohydrates burned while exercising "wasn't just coming from the breakfast that was just eaten, but also from carbohydrate stored in our muscles as glycogen".
He added: "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.
"This study suggests that, at least after a single bout of exercise, eating breakfast before exercise may 'prime' our body, ready for rapid storage of nutrition when we eat meals after exercise."
Dr Javier Gonzalez, from the University of Bath, said the study – entitled Pre-Exercise Breakfast Ingestion Versus Extended Overnight Fasting Increases Postprandial Glucose Flux After Exercise in Healthy Men – was the first of its kind.
The scientists said the long-term implications were not clear but Mr Edinburgh said studies into whether breakfast before or after exercise on a regular basis had an impact on our health were ongoing.
He added: "In particular 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.
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"These are some of the questions we will now try to answer."
The study was published in The American Journal of Physiology – Endocrinology and Metabolism.