Exercising on an empty stomach could be better for you than doing so after a meal, according to a study.
Men who had a workout before breakfast lost more fat than those who did so after the first meal of the day, scientists found.
There might be an extra benefit from exercising before eating, although further study is needed to assess the longer-term effects.
In the course of a Brigham Young University study, 18 normal-weighted and 17 clinically obese women were followed for two full days. On the first day, they exercised for 45 minutes, walking briskly on a treadmill, and then looked at 240 photographs, 120 of which were food (the other 120 were a control: flowers). The researchers then tracked the women's food intake and activity level for the rest of the day. On the second day, one week later, the women were shown the images without the workout. Again their food and exercise choices were tracked. Researchers found that both the obese women and the women at a healthy weight had a lower brain response to the images of food and moved around more following the 45 minute morning workout.
This is an obvious one, but getting your workout in before work means that you'll be up for impromptu happy hour or dinner plans. No more "I can't, I have spinning" for you!
What's more, getting your workout out of the way first means you'll actually do it. "If you work out before your day distracts you, your chances of exercising regularly go way up," Cedric Bryant, Ph.D., chief science officer of the American Council on Exercise told Women's Health.
When you exercise, the effort helps to deliver oxygen and nutrients to muscles, organs and other tissues. And that means your whole cardiovascular system will work more efficiently, upping your energy, according to the Mayo Clinic.
Exercise has both short-term and long-term brain benefits. Research shows that the short-term benefits include better executive function and memory recall. That brain boost means that a morning workout could take the place of a caffeine fix.
The study was carried out by Dr Jason Gill and Nor Farah of the Institute of Cardiovascular and Medical Sciences at the University of Glasgow.
Ten overweight men who were not regular exercisers took part in the study which looked at the effects of exercising before and after breakfast on metabolic health and fat loss.
Each man underwent three trials, up to a fortnight apart. In one, they performed no exercise then ate breakfast. The other trials saw them walking briskly for 60 minutes before eating breakfast, or doing the same walk after eating their morning meal.
Participants were given lunch three and a half hours after breakfast and the amount of fat their body burnt and the level of fat, sugars and insulin in the blood were measured over an eight and a half-hour period on each occasion.
Both periods of exercise increased fat-burning over the day, the results indicated.
But exercise before breakfast resulted in greater fat loss and larger reductions in the level of fat in the blood.
Dr Gill said: "Any exercise you do is beneficial but the indications are that there might be an extra benefit associated with exercising before eating, compared to after. However, further study is needed to determine whether the present findings extend over the long term.
"In the end we would like to encourage everyone to do some form of exercise every day. The difference between exercising before compared to after breakfast was much smaller than the difference between exercising at either time compared to not exercising at all."
The findings - in the research paper Effects of exercise before or after meal ingestion on fat balance and postprandial metabolism in overweight men - is published in the British Journal of Nutrition.