Food is off the menu for me before I exercise – even if it’s just going for a walk. It seems logical that if your stomach is empty the only place your body can get energy from is fat. Moreover, research has now revealed that exercising on an empty stomach helps people burn about 70% more fat than those who eat two hours before exercising.
But while studies have suggested the benefits of exercise could be increased when it’s done in the morning following an overnight fast, the time most people are able or want to exercise is between 4pm and 8pm.
Therefore the Nottingham Trent University researchers designed a study so that participants cycled on an exercise bike at 6.30pm for 30 minutes, before completing a time trial to cycle as far as they could in 15 minutes.
“We wanted to explore the impact of fasted exercise in the early evening, which we’d found was the most popular time for people to exercise during the week,” said Tommy Slater, a Nottingham Trent sports science researcher.
Participants cycled at 6.30pm twice on separate days – once after a seven-hour fast and once after eating a meal two hours earlier, and the amount of food participants ate at dinner was measured after exercising.
The results showed that, similar to exercise after an overnight fast, fasted exercise in the evening increased the amount of fat burned during exercise by about 70%.
And while calorie intake at dinner was about 100 calories greater for those doing fasted exercise, calorie intake over the whole day was on average 440 calories less when exercise was performed after fasting.
Researchers also found, however, that despite these benefits participants covered slightly less distance during the 15-minute time trial, and enjoyed the exercise less.
“Fasting before evening exercise might benefit some elements of health due to increasing the amount of fat burned during exercise, or by reducing the number of calories that are eaten during the day,” the report concluded.
“However, despite these benefits, fasting during the day does appear to reduce performance, motivation and enjoyment, which may make it harder for some people to stick with it in the longer term.
Dr David Clayton of Nottingham Trent University, added: “Combining exercise and fasting can be a potent way to increase benefits of exercise, so we would like to assess this over a longer period and explore other ways in which we can make fasting easier and more convenient for people.”