People who exercise before eating breakfast burn more fat than those who exercise later in the day and they don't undo the benefits by over-eating later, according to new research.
Previous studies have found exercising when you haven't eaten for hours utilises the body's fat stores, but researchers from the University of Northumbria wanted to see if it increased appetite later in the day and counteracted the benefits.
They got 12 fit men to do a 10am treadmill session –– half had eaten breakfast, the other half hadn't.
They all followed the exercise with a chocolate milkshake for recovery and were given pasta for lunch and instructed to eat until they were "comfortably full".
After assessing how much energy and fat were consumed at lunch and accounting for the energy and fat burned during the morning exercise, the researchers concluded that those who exercised before eating burned almost 20 percent more fat than those who had eaten breakfast.
The researchers also found that exercising on an empty stomach did not lead to an increased appetite later in the day or the consumption of extra calories –– suggesting it's the best strategy for fat loss.
"Exercise increases the total amount of energy we expend and a greater proportion of this energy comes from existing fat if the exercise is performed after an overnight fast," said study assistant Javier Gonzalez.
"Our results show that exercise does not increase your appetite, hunger or food consumption later in the day and to get the most out of your session it may be optimal to perform this after an overnight fast."
But sports scientist Tori Carroll explains that the most important thing for people wanting to burn fat is to find a time that best suits their lifestyle.
"The more motivated you are to work hard, the greater the opportunity to increase your total energy expenditure and post-exercise metabolic rate, which is more important than looking at purely 'fat burning' during a session," she said.
Carroll usually recommends people have a small snack before a work-out to give their body ample fuel to burn.
"If you don't have enough carbohydrate or energy on board, eventually you are going to hit the wall," she said.
"You might be burning more fat, but if you had something small, you might have an extra boost to work a little harder and longer, which will ultimately affect your total energy output."
The study was published online in the British Journal of Nutrition.