Eating around workouts has always been a tricky thing. Depending on who you ask, some fitness experts recommend eating carbs before a workout for fuel, while others are told protein makes a great pre-workout meal for those who want to bulk up.
But new research from the University of Bath says if you're looking to burn fat, the best thing to eat before a workout is nothing at all. According to their study, published in the American Journal of Physiology, overweight participants who fasted before exercising burned more stored fat to fuel their exercise.
For the study, the researchers recruited 10 overweight men and monitored their blood and fat tissue as well as their fitness and resting metabolic rates. On one occasion, the scientists deprived the men of nourishment prior to making them walk on a treadmill. On another, they provided participants with a 600-calorie meal. The scientists took additional blood and fat tissue samples before and an hour after the exercise began.
Upon examining the results, the researchers found participants who ate breakfast tended to burn more calories, but those who skipped their morning meal burned more fat. But it goes beyond that. The researchers also found genes in the body behaved differently depending on whether or not food was consumed.
"After eating, adipose tissue is busy responding to the meal and a bout of exercise at this time will not stimulate the same [beneficial] changes in adipose tissue," lead researcher Dylan Thompson said in a press release. "This means that exercise in a fasted state might provoke more favourable changes in adipose tissue, and this could be beneficial for health in the long term,” he continued.
Thompson also noted, however, that more research needs to be done before fasting can be looked at as a way to accelerate fat loss. While women were excluded from the study due to the effects of the menstrual cycle on metabolism, a 2016 study from the University of Surrey found women tend to burn more fat if they eat before exercising.
In the Surrey study, men and women were given a beverage before exercising but only a few drinks contained carbohydrates. After four weeks of intense cardiovascular training, Dr. Adam Collins found that women who consumed the carbohydrate drink burned 22 per cent more fat than those who took the placebo. Men who consumed the carbohydrates, however, only burned 8 per cent more fat.